A Taste of Late-Summer Heat Returns

If you’ve been thinking, “We need to squeeze a little more summer out of this,” the weather is going to cooperate — at least for the next few days.

Today brings a much quieter and drier weather pattern to eastern Idaho and western Wyoming. Skies will clear, sunshine will take over, and storm chances will essentially disappear for the day. The atmosphere has dried out considerably as the monsoonal moisture feed retreats, leaving us with little of the instability and moisture needed to fire off afternoon thunderstorms.

For most of us, that means a classic late-August day: sunny skies, light winds and temperatures a few degrees warmer than normal. It should be an especially nice day to get outside without constantly wondering whether a thunderstorm is going to pop up over the mountains.

One of those "get outside" days

This is the kind of weather that makes you realize summer is running out of runway.

If you have kids at home, this may be the week to squeeze in one more trip to the lake, another evening at the park, a bike ride, a backyard barbecue or a final mountain adventure before school routines take over again.

Across eastern Idaho, the Snake River Plain should feel increasingly warm through the afternoon, while communities closer to the mountains will enjoy somewhat cooler temperatures. Head toward the higher elevations and it will remain noticeably more comfortable — another reminder that in our part of the country, a short drive can mean a very different thermometer.

Western Wyoming will have that same late-summer contrast. The valleys will warm nicely during the afternoon, while the mountains remain considerably cooler. Early mornings can still feel almost autumn-like in some of the higher terrain, even while the afternoon sun is reminding us that summer isn't finished yet.

The heat starts building

The bigger story is what happens next.

Temperatures will climb a little more each day, with the warmest stretch arriving toward Friday. By then, some lower-elevation locations could push into the upper 90s, with a few spots potentially reaching or exceeding 100 degrees.

A Heat Advisory is expected Friday, with afternoon highs generally in the 94-100 degree range across the hottest locations.

That's a substantial change from the cooler mornings we've become accustomed to. The difference will be especially noticeable if you're spending the afternoon working outside, playing sports, hiking, doing yard work or simply trying to enjoy one of those long August afternoons.

And remember: high-desert heat can be deceptive. The air may feel relatively dry, but the afternoon sun is still powerful. The best strategy Friday will be to get outdoor chores and activities done earlier in the day, take breaks during the hottest part of the afternoon and keep the water bottle nearby.

Then the mountains start talking again

The atmosphere won't stay completely quiet.

As we head into late Friday and the weekend, moisture and instability begin to creep back into the region. That should bring increasing chances for showers and thunderstorms, particularly around the mountains.

This doesn't look like a washout for the weekend. Instead, think hit-or-miss summer thunderstorms — beautiful skies one minute, a dark cloud building over the mountains the next.

Mountain communities and anyone recreating in the high country should pay particular attention to changing skies. A storm doesn't have to be directly overhead to create problems. Gusty outflow winds can race away from thunderstorms and suddenly turn a calm afternoon into a blustery one.

For the valleys, we're looking at roughly a 30% chance of thunderstorms over the weekend. In other words, most of the time it should remain dry, but you won't want to completely ignore the sky.

Eastern Idaho: hot afternoons, cool mornings

For the Snake River Plain and surrounding valleys, the weekend may offer a familiar late-August combination: hot sunshine, dry stretches and the occasional thunderstorm interruption.

It will be the kind of weather where the car feels like an oven after sitting in the sun, but the evening cool-down comes quickly once the sun drops. That's one of the defining characteristics of our high-desert climate — big swings between daytime heat and nighttime comfort.

Eastern Idaho's climate is notably continental, meaning temperatures can fluctuate considerably between seasons and between day and night.

So enjoy those warm afternoons, but don't be surprised if you reach for a light jacket once you're sitting outside after sunset.

Western Wyoming: summer in the valley, fall in the mountains

Western Wyoming will have a similar story, although elevation will make the temperature differences even more noticeable.

Places such as Jackson, Star Valley and the higher mountain valleys can start the day feeling downright chilly, only to turn pleasantly warm by afternoon. In the mountains, meanwhile, the weather can change much faster.

That is very typical for late August. Climate normals show just how much temperatures vary across Wyoming's elevations, with August averages ranging from relatively warm valley locations to much cooler mountain communities.

So if you're heading into the mountains this weekend, dress for more than one season. A sunny afternoon can feel like the middle of summer, while a thunderstorm or sunset can quickly bring a reminder that September isn't far away.

The bottom line

Today through Thursday:
☀️ Sunny, dry and increasingly warm.
🌡️ Temperatures climb a few degrees above average.
💨 Winds remain generally light.
🏕️ Excellent weather for getting outside.

Friday:
🔥 Hottest day of the stretch.
🌡️ Highs around 94-100° in the warmest locations.
⚠️ Heat Advisory conditions.
⛈️ Storm chances begin increasing late in the day.

Weekend:
⛈️ Mountain showers and thunderstorms return.
💨 Gusty winds possible around storms.
🌤️ Valley storm chances around 30%, meaning plenty of dry time for outdoor plans.
🏔️ Keep an eye on the sky if you're hiking, camping, boating or recreating in the mountains.

So, for eastern Idaho and western Wyoming, summer isn't ready to leave just yet. Enjoy the sunshine and warm afternoons while they're here — but Friday's heat is a good reminder that late August can still pack a punch. And once we reach the weekend, the mountains may start providing a few reminders that the transition toward fall is waiting just around the corner.

The regional pattern also fits what we've seen climatologically: August in Wyoming often features a tug-of-war between hot, dry periods and sudden bouts of showers, thunderstorms and gusty winds.