Rex Trulove
A common saying in the United States and probably elsewhere in the world is “If you don’t like the weather in [fill in the blank with your location], just wait 10 minutes. It will change.” The weather really can change quickly and drastically, for lots of reasons. Early in 2017, in fact, Denver, Colorado, had a temperature of 80 F (26.7 C) under sunny skies on one day and it was snowing there the next day.
That is quite a change in the weather and in the temperature. However, it doesn’t come close to the greatest change. Montana has the dubious honor of having the greatest variation in temperature of anyplace in the US. In fact, it holds five US records.
Coldest temperature in the continental US
On January 20, 1954, a record cold temperature was measured for anywhere in the lower 48 states. The location was Rogers Pass, in the Montana Rockies. This pass is one of the passes over the continental divide, between Missoula, Montana and Great Falls, Montana.
The pass isn’t exceptionally high. The summit is only a little more than 5,600 feet. Yet, on that day in 1954, the temperature that was recorded was -70 F (-56.7 C). No location in the lower 48 states has ever registered a colder temperature.
Record variation for any US state
The highest temperature ever officially recorded in Montana was 117 F (47.2 C). Two locations in Montana had that temperature. One was Glendive, Montana, on July 20, 1893. The other was at Medicine Lake, Montana, on July 5, 1937.
This isn’t the highest temperature ever recorded in the US. That record is held by Death Valley, California, when it reached 134 F (56.7 C) on July 10, 1913. However, the 117 F temperatures in Montana do lead to a different record.
Since the state also has a record low of -70 F, the record high of 117 F gives Montana the record for temperature variation of any state; an amazing variation of 187 degrees F!
Greatest temperature change in a day
Another record that this state has, this time in the town of Loma, Montana, happened on January 15, 1972. Loma is a town that is northeast of Great Falls and is in the north-central part of the state.
The record happened when the temperature rose from -54 F (-47.8 C) to 49 F (9.4 C) in a single day. That is an astonishing change of 103 degrees F in only 24 hours. This isn’t just a US record, it is the greatest temperature change ever recorded anywhere in the world, in a single day.
Record for greatest change in 12 hours in the US
Fairfield, Montana, is a town of only about 700 people. it is located west by northwest of Great Falls and almost directly north of the state capital of Helena, Montana. It isn’t an extraordinary town, but something happened there on December 14, 1924, that was pretty extraordinary.
At noon in Fairfield, the temperature was 63 F (17.2 C). This is relatively balmy for Montana in December. It didn’t stay balmy for long. At midnight, the temperature was -21 F (-29.4 C). The change of 84 degrees F was the largest ever recorded in the United States in a 12-hour period.
Fastest temperature change in the US
This record is much in keeping with the “if you don’t like the weather here, wait 10 minutes”. It happened in Great Falls, Montana, at the airport, on January 11, 1980. It was definitely the fastest temperature change ever recorded in the US.
The temperature had been holding steady at -32 F (-35.6 C) when it suddenly started to change. Incredibly, in just seven minutes, the temperature rose to 15 F (9.4 C), a whopping difference of 47 degrees F. That is a change of over six degrees per minute.
The cause of the extremely fast temperature change was the Chinook winds flowing down the east side of the continental divide. Chinook winds are foehn winds that are hot and dry, though they aren’t isolated to the Rockies. In this instance, though, the Chinooks came off the Rocky Mountains, causing the enormous temperature change.
Next time you feel the urge to think that your temperatures have been changing quickly, please remember these truly large changes. Even more interestingly, all of these records were set near or in the city of Great Falls, Montana. It makes me rather glad that I live on the west side of the continental divide.
This was awesome! Records are fascinating here.
I agree. It is hard for me to imagine a change of 47 degrees in 7 minutes. The 70 below is also hard to imagine. Two years ago, we got down to -44 with a 15 mph wind. That was cold enough for me. I don’t need to experience the 70 below. lol
I always learn something in your posts. Thanks for sharing the wisdom.
Thank you for the compliment, It really isn’t wisdom, though, just knowledge. :))
I remember studying the Chinook effect for Geography O-level nearly 50 years ago – how could I ever forget the dry adiabatic lapse rate?!
The effect on temperatures is nothing short of amazing. The huge fires in southern California that happen every two or three years are nearly always fanned by the Santa Ana winds, which is the same effect.
Fascinating article, Rex. This isn’t a topic I’ve thought much about.
I have, primarily because I live in Montana. LOL When it gets cold here, it really gets cold.
Yeah, my wife and I were going to vacation out there one fall but circumstances prevented it. When we would have been there, it would have been very cold and snowy, neither of which are we big fans of.
If you ever visit, my suggestion would be early summer, like June. There is a lot to see, the weather is usually good, and you have a chance to relax without freezing into a solid block of ice. LOL It gets hot in the summer, but there are plenty of streams, rivers, and lakes to cool off in.