Astronomical fall officially begins today, but temperatures will feel more like summer across southern Idaho this week. A few showers and thunderstorms are possible Tuesday before temperatures climb through Thursday, followed by a significant cooldown heading into the weekend.
This afternoon, showers and thunderstorms are possible, especially across higher terrain and portions of south-central Idaho. Most storms are expected to remain fairly weak, but any shower or thunderstorm could produce gusty outflow winds up to 45 mph. Lightning, small hail, and brief heavy rain will also be possible. Activity should begin winding down around sunset.
Warmer and drier weather takes over Wednesday before temperatures jump even higher Thursday. Thursday is expected to be the hottest day of the week, with temperatures running around 10 to 15 degrees above normal. Many lower valleys could reach the low to mid-90s.Winds will also increase Thursday afternoon, especially across the Snake Plain. Sustained winds of 15 to 25 mph with gusts up to 35 mph will be possible. The combination of hot temperatures, dry conditions and stronger winds could lead to elevated fire weather concerns.
A strong cold front arrives Friday, bringing a major change just in time for the weekend. Gusty winds will be the biggest concern, with some areas potentially seeing gusts of 30 to 45 mph. Rain chances will favor southeast and northeast Oregon along with the mountains of central and northern Idaho, while much of southwest Idaho is expected to stay drier. Temperatures will drop behind the front, cooling around 5 to 10 degrees Friday and another 10 to 15 degrees by Saturday.
Highs this weekend will be much more fall-like, generally around the 70s in the lower valleys with 50s and 60s across higher-elevation communities. Cooler weather will stick around through early next week, with another chance of showers across northeast Oregon and north-central Idaho Sunday into Monday.
Treasure Valley Extended Forecast
