Regions of Montana

Billings sits where the Yellowstone leaves the mountains, under the Rimrocks, and gets the best of both: chinooks off the Beartooths that can put a January afternoon in the 50s, and a plains cold front behind them that takes it all back overnight. Red Lodge and the Beartooth Highway hold snow into June; the valley floor rarely holds it past a week.

Missoula is the first Montana valley the Pacific reaches. West of the Divide the winters run milder and greyer than anywhere east of it, the valleys hold inversions for weeks in January, and August is fire season — smoke from Idaho and the Bitterroot settles into the same bowls the cold air does. The Bitterroot, running south to Darby, is the state's banana belt.

The Flathead is the wettest, snowiest, cloudiest corner of Montana, and it is the corner people picture when they think of it. Glacier's west side takes better than a hundred inches of snow at the park entrance and several times that on the passes; the Going-to-the-Sun Road opens in late June or July and closes when the first real storm says so. Flathead Lake keeps the shore a few degrees off either extreme.

This is chinook country. The Front stands the westerlies straight up and sends them down the other side warm and dry, and Great Falls is where the record books keep the results: 47 degrees in seven minutes at Loma in 1972, still the fastest temperature change ever measured, and winter afternoons that go from 10 below to 40 above between lunch and dark. When the chinook fails, arctic air pools against the same mountains and Cut Bank posts the coldest reading in the country.

Helena sits in a valley at the foot of the Divide with the mountains on three sides, and that is its forecast: less snow than the passes above it, more wind than the Missouri below it, and a cold pool in January that the sun cannot reach until noon. MacDonald Pass, ten miles west on US-12, is a different climate with its own road report.

Bozeman is the fastest-growing place in Montana and the snowiest valley town in it: Bridger Bowl runs on cold smoke that the Gallatin Valley gets a taste of most weeks from November to April. Livingston, one pass east, is the windiest — the Yellowstone canyon funnels the westerlies onto I-90 hard enough to close it to high-profile vehicles a dozen times a winter. West Yellowstone, at the park gate, is the cold spot of the lower 48 more mornings than anywhere but the Hi-Line.

Butte sits a mile high, on the Divide, and is the coldest city in Montana for it: the average January low is near zero and the record is 52 below. Homestake and Elk Park on I-90 and Monida on I-15 are the passes truckers watch, and the Big Hole above Wisdom is routinely the coldest valley in the state. It is also the copper that made Montana the Treasure State — and the color of this site.

There is nothing between the Hi-Line and the Arctic. When the polar air comes south it arrives here first and stays longest — Havre, Glasgow and Scobey trade the coldest reading in the lower 48 through most of January, and the wind chill on US-2 has no windbreak for two hundred miles. Summer is the other extreme: the same open country runs to 100 and puts up the state's biggest hail.

Eastern Montana is the plains, and the plains do everything at full size: the state's hottest summers at Glendive and Miles City, its hardest hailstorms, its blizzards that close I-94 from Billings to Bismarck, and the flash floods that take out the same county bridges every decade. The Big Open around Jordan is the emptiest country in the lower 48, and the forecast there comes from a radar two hundred miles away.