Helpful Links:

Favorites – Weather Forecasts

Current US Radar Map

Forecast US Radar Map

Lightning Risk & Strikes Map

Hail Size Map

Current Air Quality Map

Smoke (High-Res) Surface Map

Smoke (High-Res) Sky Map

Big Picture Weather Pattern:

An area of high pressure will set up in the Four Corners area, while monsoonal moisture will surge northward into the Southwest U.S. and will circulate around the high pressure center.

This is setting up to be a more consistent monsoon pattern than we have seen all summer, and moisture will expand into the Sierra Nevada Range and eventually the Northern U.S. Rockies over time. 

Check out the 2-week rainfall projection from the European AI Ensemble Model, which is a lower-resolution average that represents the average of 50 simulations of this model. This is an impressive wet signal for much of the Western U.S.

5-Day Temperature Outlook:

Temperatures over the next 5 days will generally be warmer than average west of the Continental Divide and cooler than average east of the Continental Divide. 

The highest temperature anomalies are expected over the Pacific Northwest, where a heat wave will take hold this weekend.

Thursday (Aug 21):

The monsoon surge will begin gradually with moisture favoring New Mexico, Arizona, and Utah on Thursday. Isolated to scattered thunderstorms will develop across this region, with many storms producing only light rainfall.

However, stronger storms will be capable of producing heavy rain, and as a result, there is some risk of slot canyon flash flooding.

Further north, a cold front will slide into Wyoming with isolated to scattered thunderstorms developing. Areas east of the Divide will be the most favored, including the Bighorn Range and the Black Hills, with locally heavy rain possible. 

Friday (Aug 22):

A cold front will slide into Colorado with moisture increasing along and east of the Continental Divide, where numerous thunderstorms capable of heavy rain can be expected. This includes areas near the Divide in the Front Range, Sawatch Range, and San Juan Range. 

Further west, monsoon moisture will continue to increase across Arizona and Utah, and will also expand westward into California, including the Sierra Nevada Range and Tahoe. These areas (shaded in yellow) will see scattered thunderstorms capable of producing heavy rain. A risk of flash flooding is also expected, especially in slot canyons and burn scars.

Saturday (Aug 23):

A further uptick in thunderstorm coverage and rainfall is expected across Utah, Colorado, Nevada, California, and northern portions of Arizona and New Mexico. Storms could develop before noon over the higher peaks, and heavy rain can also be expected with a threat of flash flooding in slot canyons, burn scars, and vulnerable terrain. 

Sunday (Aug 24):

Yet another uptick in thunderstorm coverage and rainfall amounts can be expected, and coverage will also expand northward into Wyoming and into Southern Oregon. Once again, heavy rainfall will be possible with storms, and slot canyons and burn scars will have a heightened risk of flash flooding.

Monday (Aug 25):

This is shaping up to be another active day across a large portion of the West, from the Southwest to the Rockies to the Sierra. An expansion in coverage is also expected into Southern and Central Idaho. Heavy rainfall and flash flooding will remain a threat across these regions, and storms could also develop prior to noon over the higher peaks. 

August 26-30:

Next week, an active monsoon will continue with weak troughing over the West, helping to bring moisture even further north into the Pacific Northwest and Montana. The strongest wet signals for this period are currently showing up over Idaho and Wyoming, but areas throughout the Rockies, Southwest, and Sierra will be in an active pattern with significant late summer rainfall possible. 

Temperatures will be cooler than average across much of the Southwest and the Central Rockies thanks to the uptick in moisture, while a strong above-average temperature signal looks to remain over the Northwest.

In fact, we could see an increase in fire danger across the Northwest due to the combination of heat plus an increased potential for lightning on the northern fringe of the monsoon.

August 31 - September 4:

Heading into Labor Day weekend, an active pattern is expected to continue across the West, which could potentially impact holiday weekend outdoor plans.

Monsoonal moisture looks to remain over the Southwest and the Central Rockies, while longer-range models are also hinting at the arrival of Pacific disturbances, which could contribute to shower and thunderstorm chances across the Northwest and Northern Rockies. 

Near to below normal temperatures are expected to persist over the Central Rockies, while an above-normal signal remains over the Northwest, though some cooling is expected here compared to prior days.

Thanks so much for reading! Next update on Friday (August 22).

Alan Smith 

Seasonal forecast season is here!

I have been studying historical analogs for the upcoming fall and winter seasons, and have recently published outlooks for North America for the fall of 2025 and winter of 2025-2026.

More Details:

Fall 2025 Weather Outlook

Winter Forecast Preview 2025-2026