Much is said these days about temperatures, but very little is told about how those temperatures are measured. There are various types of thermometers used at established weather stations, each uses slightly different instrumentation.  Here I’ll describe the different types of thermometers used to take our temperature and how that instrumentation has changed over the years.

(Additional content was added to this post on July 31st, 2024)

A Brief History of Taking our Temperature

Daniel Gabriel Fahrenheit invented the first Liquid-in-Glass (LIG) thermometer in 1714. He started out using alcohol and then switched to mercury filled thermometers. An alcohol thermometer is preferred, especially in colder climates, because mercury freezes at minus 39 degrees.

Around 1850 the U.S. Weather Bureau began taking daily readings of temperature using Liquid-in-Glass thermometers at official weather stations. Most of those stations were in the eastern half of the United States at that time.

By the late 1870’s these weather stations began using two LIG thermometers, one that registered a maximum temperature and one that registered a minimum temperature. These thermometers were read once a day by a trained weather observer, to get a maximum and minimum temperature for the previous 24-hours and were reset manually each day.

By the mid-1880’s the standard was for these thermometers to be housed in a Stevenson Screen, later known as a Cotton Regional Shelter. These shelters were essentially large, white, louvered wooden boxes that protected the thermometers from wind, rain, and direct solar radiation. The shelters were also designed to allow good ventilation to negate any artificial overheating inside the shelter.

Fast forward another 100 years to the mid-1980’s, when the National Weather Service began changing the existing instrumentation over to an electronic thermometer. These could log temperature readings automatically, eliminating the daily routine of reading and resetting the thermometers. This provided a more consistent recording of the data, with fewer missed days in the daily weather records.

By the late 1990’s, about two-thirds of all official weather observing stations across the U.S. had been changed over to electronic thermometers. Today, almost 100-percent of the official thermometers maintained by the National Weather Service are electronic.

Electronic Thermometers

The modern Maximum-Minimum Temperature Sensor (MMTS) used today is an electronic RTD type thermometer, or Resistance Temperature Detector, which measures electrical resistance in a coiled metal wire.  As temperatures rise or fall, electrical resistance rises or falls, in a linear fashion.

The RTD-type thermometers used at official weather observing stations today have proven to be as precise as the LIG-types, both are accurate to within about 0.5 degrees F. The biggest difference is that RTD thermometers have a much faster response time than LIG thermometers. Which means, brief spikes in temperature, high or low, will be recorded by an RTD. An LIG thermometer cannot record those spikes, as it takes longer for the liquid to react.

RTD thermometers are more sophisticated, more accurate, and more stable than simple thermistor-type thermometers, like you would find in a home weather station or your car. Many of the remote weather stations in the mountains utilize a thermistor-type thermometer, which in many cases are not shielded properly and susceptible to erroneous readings, like your car’s thermometer is.

The new MMTS thermometers are not housed in the old type of shelter, but rather inside a beehive shaped, vented canister. Which, I have discovered, the size of the beehive canister is not standard from one weather station to another. That creates an issue, which I will expound upon shortly.

Jackson, WY Instruments

The earliest official weather readings here in Jackson, WY began in 1899, although only for about a month. By 1916, the primary weather station in town, located behind the Forest Service office on North Cache Street, began taking more regular readings. But it wasn’t until about 1950 that records became more consistent year-round. Back then, and until the early 2000’s, LIG-type thermometers were used.

In March of 2002 the Jackson Climate Station switched over to an electronic MMTS thermometer.  In October of 2012 the station moved a few hundred yards to the North, to behind the Visitor Center.

Because Jackson’s weather station has always bordered the natural setting of the Elk Refuge and has been in roughly the same location for over 100 years, I believe the Jackson Climate Station has one of the best long-term temperature records available anywhere in the country.

A weather station that has remained in a more natural setting, away from concrete, asphalt pavement, and large buildings, provides more realistic historical temperature readings. Jackson’s station is unlike most weather stations around the U.S., which have seen big cities grow up around them.

Jackson vs. Moose Wyoming Instruments

I have resided in the Jackson Hole valley for over 40 years now and in that time, I have observed and researched our weather and climate, about as extensively as anyone could. Over the years I have seen some changes, not only in the weather, but also in the instrumentation used to measure temperatures.

While analyzing monthly weather data from the Jackson Climate Station, located on the north end of town with the Moose Climate Station in Grand Teton National Park, I discovered that a change in equipment yielded different results. Somehow Moose had become warmer than Jackson, on certain days, which historically has never been the case. Allow me to explain why.

The Stations

Both Jackson and Moose are Cooperative (COOP) weather stations established and maintained by the National Weather Service. Each day, trained weather observers take readings from these weather stations and submit the data to the National Weather Service, which is then transmitted to the National Climatic Data Center.

Both Jackson and Moose have long-term records, and these records establish what we refer to as our climate, the compilation of monthly averages over a minimum of a 30-year period. They are also the stations referenced when a new record high or low temperature is established.

Jackson’s station has been in roughly the same location since the early 1900’s. The Moose weather station was originally located at Beaver Creek, then in 1958 it moved to Moose, behind the Park Headquarters building. In 2018 the station moved across the road, close to new Visitor Center.

Jackson switched from Liquid-in- Glass to a digital-type thermometer in 2002. Moose changed equipment when the station moved in 2018.

The Moose station now sits over dirt and sparse sagebrush, whereas the Jackson station sits over grass. The underlying surface can influence temperatures, as dirt heats up more readily than green grass. Initially, when I observed that Moose was recording higher daytime temperatures than Jackson, I thought it was because of the Moose station’s new location. Further investigation led me to a different conclusion.

Size Matters

Where these two weather stations now differ is in the housing that shields the thermometer. The “beehive” housing that protects the thermometer is supposed to be of a standard size. The Jackson housing, made by Airflo, meets the NWS standard. The Moose housing, made by Nimbus, is about half the size of Jackson’s housing. I am not sure why or how that happened. The NWS told me there was a vendor change before the Moose station was installed.

Why is this important? Because thermometers need good air flow around them to get an accurate reading of the true air temperature. A larger housing allows better ventilation, or aspiration. A smaller housing does not allow good aspiration and can lead to higher temperature readings, most notably on sunny days, with calm winds.

This became glaringly evident when I saw the average monthly high temperatures in August of 2018 that were nearly 5 degrees warmer in Moose than they were in Jackson. On the warmest and driest days of that month, Moose had daily high temperatures that were 9 to 11 degrees warmer than Jackson’s. That is just not realistic.

Going back to a time when Liquid-in Glass thermometers were being used, I looked at the records from August 1988, one of the hottest and driest summers up to that point. What I found was that Jackson’s average high temperature that month was about 2 degrees warmer than Moose. On the warmest days of that month, Jackson had temperatures that were 5 to 8 degrees warmer than Moose. That’s much more reasonable.

So, between 1988 and 2018, Moose changed from being about 2 degrees cooler than Jackson in August to being almost 5 degrees warmer than Jackson in August.

I can only speculate that the discrepancy is in the size of the housing and how well they are able to aspirate. A smaller thermometer housing yields higher temperatures on a sunny day than the same type of thermometer housed in a larger beehive.

There is one more thing that might have been affecting the Moose thermometer, and that is the fact that it is a wireless system, it requires a solar panel to keep the battery charged. Unfortunately that panel is very close to the thermistor housing and may be adding additional heat to the max temp readings, especially on those sunny days!
(See photo below).

Further investigation showed that overnight low temperatures, temperatures on cloudy or rainy days, and wintertime temperatures when there was snow on the ground, were less affected, and little discrepancy was noted.

The problem with this change in thermometer types the last 20 years, and more so with the discrepancy between thermometer housing sizes, is that our temperature records are no longer consistent. Those inflated high temperatures in Moose become part of the long-term record and comparing them to records prior to 2018 has become apples and oranges.

(Note: The Moose thermometer has been inoperable and not recording temperatures since May 23rd, 2024. I am told by the NWS they are working on fixing that. Hopefully they switch out the beehive to one that is closer to the standard size specified by the NWS, and also move the solar panel further away from the thermometer too!)

It makes me wonder what other weather stations around the country are experiencing a similar effect with their newer instrumentation as we are seeing here in Jackson Hole.

As Robert Mallet said in the Manual of Scientific Inquiry, back in 1859, “Nature, rightly questioned, never lies.”

Post by meteorologist Jim Woodmencey

It was a slow start to the Winter of 2023-24, but a big February and record March snowfall saved our winter. The winter ended with above average snowfall in both the Jackson Hole valley and up in the mountains.

Think back to how grim the winter was looking around here all through December and into the first week of January. The Town of Jackson only had one inch of settled snow on the ground on New Year’s Day. The average snow depth that time of year in town is around 8 inches.

The mountains were also looking skinny, snowpack-wise. The upper elevations at the Jackson Hole Mountain Resort only had 36 inches of snow on the ground on January 1st, 2024. The average depth there on that date is 58 inches. The base of the mountain only had 5 inches of snow on the ground on New Year’s Day, and the historical average there is 22 inches.

Click here to view video…skiing on Teton Pass 29DEC2023

Mid-January brought some hope and relief, but it was February and March that piled it on. Read on for a complete review of the winter’s snowfall numbers and how they compared to years past and the averages.

Town Snow

Winter began almost bone dry. Very little snow fell in November and December’s total snowfall in town was less than 6 inches, compared to an average snowfall in December of 17 inches.

A couple of good storms mid-January gave winter a much-needed shot in the arm, ending the month with 21.9 inches of snowfall, which is just above the average January snowfall in town of 19 inches.

February 2024 added another 34.6 inches of snowfall in town, making that the third snowiest February on record in Jackson. Only February of 2019 with 55 inches and February of 1999 with 44 inches had more than this past February.

March came in like a lion and went out like a lion. On March 1st to 2nd, 2024, Jackson broke a 24-hour snowfall record, with 17 inches of accumulation in town. That is the most snow ever recorded in one day during the month of March in Jackson. The previous record was 14 inches on March 25th, 1907.

March continued to roar, ultimately breaking the monthly snowfall record with a total of 33.9 inches. That beat out the old record for March snowfall of 32.8 inches, set back in 1938.

Total Snowfall for the four months of winter, December through March in Jackson was just over 96 inches, 96.2 inches to be exact. That is 157-percent of the average winter snowfall in Jackson of 61 inches. Surprisingly, this winter also bested last winter’s December through March snowfall total in town of 83 inches.

Jackson also measured 7.11 inches of water in that snow. That is 132-percent of the average December through March precipitation amount of 5.39 inches. This winter was also wetter than last winter, the December through March precipitation in 2022-23 was 6.50 inches.

Mountain Snow

Snowfall in the mountains this winter during the “ski-season”, from December 1st to April 1st, ended up above average. The Rendezvous Bowl study plot at around the 9,600-foot elevation at the Jackson Hole Mountain Resort tallied 360 inches for December 2023 through March 2024. That is more than the long-term average of 312 inches for that time period, but nowhere close to the record-breaking snowfall total of the previous winter, which had 443 inches from December through March 2022-23.

It was February and March this year that picked up the slack. February 2024 had 131 inches of snowfall at the Rendezvous Bowl site, making it the 5th snowiest February there in 49 seasons. March of 2024 had 99 inches of snowfall, tying it with March of 2018 for the 7th snowiest March on record.

JHMR also broke their one-day snowfall record on March 1st to 2nd, 2024 at Rendezvous Bowl, with 31 inches of snow recorded at Rendezvous Bowl in a 24-hour period. That blew away the old one-day snowfall record of 26 inches from December 23rd to 24th, 2008.

Snow Summary

Last winter had an earlier start, with snow beginning in November, and basically never letting up, with every winter month seeing above average snowfall.  This winter had a later start, with well below average snowfall in November, December and into January. Then in February and March of this year winter finally kicked in, outperforming the previous year.

February and March of 2024 had a combined total snowfall just shy of 69 inches in the Town of Jackson, compared to February and March of 2023 which had 41 inches combined. Both years were well above the long-term average total snowfall for the two months of 25 inches.

In the mountains, Rendezvous Bowl recorded a total of 230 inches of snow this February and March, whereas the combined total snowfall for February and March of 2023 was 211 inches. The average snowfall at that location for February and March combined is 140 inches.

Although it came later, overall, the winter of 2023-24 still ended up a snowier than normal winter, both in town and in the mountains.

Jim is the chief meteorologist at mountainweather.com and has forecast the weather in Jackson Hole for over 30 years.

Note: This post originally appeared in the Jackson Hole news & Guide April 17th, 2024 issue.

Is there such a thing as a typical El Niño or La Niña?

Every year there is always a lot of talk about El Niño and La Niña and how it might affect the weather, especially our winter snowfall. The terms have become quite commonplace, although I suspect most people don’t fully understand what these terms mean.  We just assume that whatever is going on with the weather is because, “It’s an El Nino year”, or “It’s a La Nina year”.

This winter started out warm and dry in Jackson. Blame that on El Niño, right? Then, it started snowing in mid-January, followed by the major dump of snow we just had mid-February. Do we also blame that on El Niño? Well, consider this, we now have a deeper snowpack in town and in the mountains than we had last year at this same time, when it was a La Niña year.

Let’s take a closer look at what defines an El Niño or a La Niña and what other things influence the weather we get from one winter to the next.

ENSO

El Niño and La Niña are part of what is known as the El Niño Southern Oscillation, or ENSO. There are three phases to ENSO that are based on the sea-surface temperatures in the Equatorial Pacific. El Nino is the warm phase, La Nina is the cold phase, and then there is a neutral phase, when sea surface temps are closer to normal, I’ll call that a No Niño. These conditions develop over a period of months and may last from 3 to 12 months, or longer.

ENSO conditions go back & forth between warmer and colder every few years. Some events are stronger, although the majority are weaker events.

Stronger events tend to have more of an impact on the weather patterns across the Northern Pacific Ocean during the winter months and are often loosely correlated with areas of above & below normal snowfall in the Western United States.

El Niño

Our current El Niño began early last fall and is now expected to weaken as we head towards spring, El Niño conditions occur when warmer than normal sea-surface temperatures exist across the Equatorial Pacific. Easterly trade winds on either side of the equator become weaker during an El Niño, which is caused by a weakening pressure gradient between the eastern Pacific & western Pacific (between Peru and Australia). Weaker trade winds allow warmer surface water to surge eastward, replacing the normal cooler water off the coast of South America.Typically, during El Niño winters the Southwestern U.S is cooler & wetter than normal, and the Northwestern U.S. is warmer & drier than normal. In Jackson, historically, El Niño winters have not been our snowiest winters.

La Niña

Last winter, and the previous two winters before that, we were under La Niña conditions. La Niña conditions occur when sea-surface temperatures across the Equatorial Pacific are colder than normal. During a La Niña the Easterly trade winds are stronger, causing cooler water in the eastern Pacific to spread westward, allowing the upwelling of even colder water along off the coast of South America.Typically, during La Niña winters the Northwestern U.S. is cool & snowier than normal, and the Southwestern U.S is warmer & dry.

In Jackson, the majority of our biggest winters, like last winter’s record snowfall in the mountains, came under a La Niña. However, untypically, record snowfalls occurred throughout the Western U.S. The year before that was also a La Niña winter and Jackson had below average snowfall, as did many other areas across the West.

UCLA Study

A recent study by scientists at the University of California, Los Angeles and the California Institute of Technology, found that using ENSO to predict the winter seasonal outlook and the amount of California’s precipitation is unreliable. Their study found that ENSO only plays a minor role for total CA precipitation; instead, a majority of CA precipitation is independent of ENSO and more closely associated with the atmospheric wave patterns that develop over the North Pacific.

The study went on to say, “historical records suggest that ENSO only explains about 30-percent of the year-to-year variability of CA winter precipitation”.

Since long-range winter outlooks rely heavily on the condition of the ENSO, it might be prudent to look beyond just that particular oscillation.

Other Oscillations

Ocean circulations and water temperatures drive our weather. ENSO is just one piece of that bigger puzzle. Stronger storms tend to develop where there are bigger differences in temperature, between the North Pacific Ocean and the Equator, for instance. And also, across the North Pacific, from west to east.

While El Niño and La Niña get all the press, there are other oscillations going on in the oceans that you never hear about, which also affect the weather patterns in the Pacific and around the globe. Such as, the Pacific Decadal Oscillation (PDO), the Pacific North American Pattern (PNA), the North Atlantic Oscillation (NAO), the Arctic Oscillation (AO), the Indian Ocean Dipole (IOD), and the Madden-Julian Oscillation (MJO), to name a few.

Some of these oscillations last several years, some a few days to weeks, but they are all interacting with whatever phase ENSO happens to be in and dictating where storms develop and where they track.

I hope you can now understand that the weather we get depends on more than what is happening with ENSO. The last few winters are good examples of why you don’t want to pin the blame on just one thing. It is the complex coupling of atmospheric and oceanic circulations, and their many oscillations, that ultimately determine the weather we receive. All of that is constantly changing, which is what makes meteorology so fascinating, and challenging.

Posted by meteorologist Jim Woodmencey