By CHUCK PARRETT, retired USGS Hydrologist
You’ve undoubtedly heard some of the jokes about Montana winters, such as: “Yes, Montana has four seasons—almost winter, winter, still winter, and road construction;” or “You know you’re in Montana if you have to make your kid’s Halloween costume large enough to fit over her parka;” blah, blah, blah.
Yeah, Montana winters are cold alright. The coldest temperature ever recorded in the lower 48 was -70 on Rogers Pass between Great Falls and Missoula in January 1954 (even Montana can’t outdo our 50th state near the arctic, though, where it once reached -80). Not only does Montana have the record low temperature outside Alaska, there have been nine official recordings of temperatures below -60.
Only Utah, Colorado, and Wyoming have as many as two official readings that low, while Idaho, Minnesota, and North Dakota each have one reading of -60 or lower. Just because I know you’re curious, Alaska has 19 recorded low temperatures of -70 or colder!
It’s not only cold here, but it can turn dramatically colder pretty dang quickly. Browning holds the world record for the greatest temperature drop in 24 hours, where in January, 1916 the thermometer plummeted from a balmy 44 to a teeth-chattering -56.
Ironically, Montana also holds the world record for the greatest temperature rise in 24 hours, when Loma saw the thermometer rise 103 degrees from a shivery -54 to a comparatively scorching 49 in January, 1972.
The rapid temperature fluctuations are due to stationary fronts that move quickly along the eastern flanks of the Rocky Mountains.
The warm fronts from the southwest that move northward along the mountains are called chinooks and provide welcome relief from the bitter cold.
The cold fronts that move quickly south bringing bone-chilling nastiness probably also have names, but they likely can’t be repeated in a family-oriented newspaper.
So, with these low-temperature stats, you’d think Montana ought to be considered the coldest state in the lower 48, right? Well, maybe.
Montana is a big state with widely varying topography and weather, so we have to use weather data from a lot of different locations statewide and average them to come up with a ”cold” number that is representative of the state as a whole.
That also applies to all other states we want to compare with Montana. We also want to make sure the data for all states are from some common, long-term period, so we’re sure our “cold” number is indeed comparable with their “cold” number.
Luckily, the U.S. Weather Service computes and compiles weather statistics for 30-year time periods, such as 1971-2000, so we could use that as a basis for comparison. We also have to decide what this “cold” number is that we want to measure and compare.
One way to do that is to average the daily minimum temperature with the daily maximum temperature at every weather station to get a daily average. Then a reasonable “cold” number would be this “averaged” daily temperature averaged again over some time period, like a year or maybe just the winter season of December through February.
I like the idea of just using the winter months, because we’re looking to find the coldest state, and using daily average temperature during the warm weather months doesn’t make a lot of sense to me. Who cares who has the coldest July, right? OK, so let’s use just the winter months of daily average temperatures.
To determine a statewide average “cold” then, we average that daily average temperature for just December, January, and February at all stations to determine a single figure for Montana’s average temperature during the winter season.
Do the same for other states, and we can finally compare to see who wins the title of “coldest” state in the lower 48 (we’ve conceded the “coldest state in the country” title to Alaska).
Now, luckily for a moderately lazy old-timer like me, these data have already been compiled for 1971-2000. Are you ready?
The coldest state south of Canada is (drum roll, please)—North Dakota, with an average winter temperature of 12.2 degrees.
The next coldest is Minnesota, with an average winter temperature of 12.4 degrees.
Then comes Maine with a temperature of 16.8. So, what the heck, where is Montana?
Well, it comes after Wisconsin, Vermont, South Dakota, and New Hampshire. Yep, that’s right, Montana comes in at a paltry 8th coldest, with an average winter temperature of 21.2 degrees. How can that be, you ask, with all those record low temperatures described above?
Well, we can partly blame it on the Rocky Mountains, where those winter-time warm chinook winds often disrupt cold spells in Montana. Our generally flatter sister states to the east, especially North Dakota and Minnesota, have cold spells that often seem to last most of the winter. Another factor is that our large state is almost 700 miles wide from east to west, and the western third is more affected by warmer weather systems moving east from the Pacific than is the eastern two-thirds lying mostly on the east side of the Rockies.
So, you can win some bets and trivia contests at the local pub with some of the above data on record lows and rapid temperature changes in Montana, but be leery of betting that we’re the coldest state.
Just to give you some more ammo for your next trivia contest, here are a few more obscure Montana weather records I gleaned from various places: The temperature range from maximum recorded to lowest recorded in Montana is 187 degrees ( 117 to -70).
We barely beat out Utah with a range of 186 degrees (117 to -69). North Dakota is third with a range of 181 degrees (121 to -60), and Alaska is a measly fourth with a range of 180 degrees (100 to -80). These data are from official National Weather Service Records. According to the Guinness Book of World Records, the largest known snowflake was measured at 15-inches by a rancher near Fort Keogh, Mont., in 1887.
No corroboration or photos exist for this one, though. Finally, the highest barometric pressure recorded in the lower 48 states was 31.42 inches at Miles City on Christmas Eve in 1983.
Good luck, and stay warm! MSN