Pack a parka. Now grab a t-shirt. Honestly, that’s the reality of waking up in the world’s first national park. People think they’ve got the Rockies figured out, but Yellowstone is its own beast, sitting on a high plateau where the sky does whatever it wants. You might see a blizzard in July or a 50-degree day in January.
It’s wild.
If you’re trying to pin down Yellowstone National Park weather by month, you have to realize the park doesn’t follow a standard calendar. It follows the snow. Most of the park is over 7,000 feet above sea level. That height changes everything. It means the "growing season" for plants is barely 60 days long. It means the difference between the North Entrance in Gardiner and the South Entrance near Jackson can feel like two different planets.
The Reality of Yellowstone National Park Weather by Month
Let's get into the nitty-gritty. You’ve probably seen those tidy little charts online. They’re usually wrong because they average the whole park. Mammoth Hot Springs is much lower and drier than the Bechler region or the East Entrance. Here is what actually happens on the ground.
January: The Deep Freeze
This is the heart of winter. Highs struggle to hit 24°F, and lows? They routinely dip to 0°F or way below. In 1933, it hit -66°F near West Yellowstone. That’s not a typo.
You can’t drive your car to Old Faithful. Everything except the road from Gardiner to Cooke City is closed to regular wheels. You’re on a snowcoach or a snowmobile. The air is so cold it turns the geyser steam into "diamond dust"—tiny ice crystals that float in the air like glitter. It’s breathtaking, but your nose hairs will freeze.
February: Snow, Snow, and More Snow
It’s slightly warmer than January, maybe hitting 28°F on a "hot" day. This is peak mating season for wolves. Because the snow is so deep, the elk are pushed down into the valleys, making them easy pickings. If you’re a photographer, this is your month. The white backdrop makes everything pop. Just don't expect to go for a casual stroll; you'll need snowshoes or you'll be post-holing to your waist.
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March: The False Start
March is a tease. You'll get a day that hits 40°F, and you’ll think spring is here. It isn't. It’s still winter, just messier. This is when the grizzly bears start waking up. They’re hungry and looking for winter-killed carcasses. The park starts closing the over-snow travel (snowcoaches) mid-month to begin plowing for the summer season. Basically, the park goes into a weird limbo.
April: Mud and Calves
April is "Mud Season." The snow is melting, the rivers are rising, and the roads are mostly closed until the end of the month. Highs reach the high 40s. This is when you see the "red dogs"—baby bison. They are everywhere in the Lamar Valley. It’s a great time to visit if you don’t mind grey skies and limited services, because the crowds haven't arrived yet.
May: The Awakening
Finally, things get green. Highs hit 50-60°F, but it still drops below freezing at night. May is the wettest month in Yellowstone. Expect rain, expect sleet, and expect a random 10-inch snowstorm just to keep you humble. Most roads open by mid-May, but Dunraven Pass usually stays closed until the very end of the month.
June: High Altitude Spring
June is gorgeous but crowded. The wildflowers—like glacier lilies and shooting stars—erupt. Highs are in the upper 60s. The waterfalls, like the Lower Falls of the Yellowstone, are at their absolute peak flow because of the snowmelt. It’s loud, it’s powerful, and it’s spray-heavy. You still need a heavy jacket for the mornings.
July: The Peak
This is the only month where you can reasonably expect to wear shorts. Highs average 79°F, though it can hit 90°F in the lower elevations. It’s dry. The mosquitoes are also at their peak, especially near Yellowstone Lake. This is when the bison rut (mating season) begins. You’ll hear the bulls grunting like lions. It’s loud.
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August: The Burn
August is similar to July but drier. Thunderstorms are common in the afternoons. These "dry" lightning strikes often start fires. Don't be surprised to see a haze of smoke in the air. Highs stay in the high 70s, but by the end of the month, you’ll feel a sharp chill as soon as the sun drops behind the mountains.
September: The Secret Season
Honestly? September is the best month. The crowds vanish after Labor Day. The elk rut begins, and the sound of bull elk bugling through the mist at Mammoth Hot Springs is something you never forget. Highs are a perfect 60-65°F. The aspens turn gold, usually peaking in the last week of the month.
October: The Gamble
October is for the brave. You might get a week of "Indian Summer" with 50-degree days and blue skies. Or you might get a blizzard that shuts the roads down for the season. Most park lodging closes in October. By Halloween, the interior roads are closed to cars. It’s quiet, lonely, and beautiful.
November: The Grey
November is the "ugliest" month, if Yellowstone can be ugly. It’s not quite winter enough for snowcoaches, but it’s too snowy for cars. It’s windy, cold (highs of 33°F), and dark. The park is basically closed to everyone except those driving the northern road.
December: The Winter Wonderland
By mid-December, the snowcoaches are back. The park transforms into a Narnia-like landscape. Highs are back down to 20°F. Christmas at Old Faithful Snow Lodge is a bucket-list item, but you’ve gotta book it a year in advance.
What Most People Get Wrong About the Weather
People see a forecast of "70 and Sunny" for West Yellowstone and think they’re set. They aren't.
First off, temperature swings are violent. I've seen it drop 40 degrees in two hours. If the sun goes behind a cloud at 8,000 feet, you will feel it instantly.
Second, the wind. The "Pitchstone Plateau" and "The Gallatins" act like funnels. You can have a calm day in the Hayden Valley while the Beartooth Highway is getting slammed with 50 mph gusts.
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Third, the sun. The air is thin. You will burn faster in 60-degree weather in Yellowstone than you will in 90-degree weather in Florida. Wear the sunscreen. Trust me.
Packing for the Chaos
Since the Yellowstone National Park weather by month is so fickle, your packing list shouldn't change that much between May and September.
- Layers are the law. A moisture-wicking base (no cotton!), a fleece or wool mid-layer, and a waterproof shell.
- Proper boots. Sneakers are fine for the boardwalks, but if you're hitting the trails in June, they'll be muddy. In October, they'll be icy.
- Gloves and a hat. Even in July. If you’re out at dawn watching wolves in the Lamar Valley, it will be in the 30s. You’ll want those gloves.
Actionable Steps for Your Trip
- Check the NPS Road Map daily. Weather doesn't just affect your comfort; it closes roads. A mudslide or heavy snow can turn a 2-hour drive into a 6-hour detour.
- Download the "NPS Yellowstone" app for offline use. Cell service is non-existent in the heart of the park.
- Target the "Shoulder" hours. No matter what month it is, the weather is most dramatic and the wildlife is most active at dawn and dusk.
- Book Gardiner or Cooke City for winter. If you want to drive your own car and see wolves in January or February, the North Entrance is your only gateway.
Yellowstone doesn't care about your itinerary. It’s a high-altitude wilderness that dictates the terms. If you go in with the mindset that "there is no bad weather, only bad clothing," you’ll have the time of your life. Just keep an eye on those clouds—they move fast.