It’s officially fall, but when will summer release its heated grip over Boise? Not soon...
Boise, welcome to fall.
Wait, what?
The Autumnal Equinox at 7:04 p.m. on Thursday signaled the astronomical start of fall — meteorological fall starts on Sept. 1 to make record-keeping easier — bringing hopes of cooler weather, hot cups of cocoa and the return of your cold-weather wardrobe.
But then Boise’s record-breaking summer reared its head again, forcing temperatures to spike into the 80s for the foreseeable future, dashing any hopes of fuzzy socks and cold, overcast mornings for the time being.
So, is summer here to stay? Will Boise residents ever experience the touch of cold air on their skin again?
Eventually. But it’ll take at least another week, according to forecasts by the National Weather Service in Boise.
“On Thursday, we’ll start to slightly cool down a little bit,” Weather Service meteorologist Sophia Adams told the Idaho Statesman. “We’re not sure exactly when we’ll start cooling down because we’ll have another trough moving into the region. But forecast models are still a little bit all over the place for when that trough will get here.”
Boise’s forecast… why is it so hot?
Boise did get a brief taste of fall on Thursday. The temperature peaked at around 70 degrees while the low temperature dipped into the 40s.
But temperatures are forecast to rebound drastically over the weekend. The Weather Service forecasts a high of 81 degrees on Saturday, and temperatures will get as high as 88 degrees by Tuesday before gradually cooling down to the low 80s.
The brief period of cool weather and storms that passed through Boise on Wednesday and Thursday was because of an upper-level low-pressure system, also called an upper-level trough, according to Adams. An upper-level low is a cold-weather system high in the atmosphere — when it passes over an area, it pulls warm air up into it, causing cooler temperatures and storms.
But an upper-level ridge — which typically brings fair and clear weather — is building to the east and will bring temperatures above normal once it passes through Boise.
“We’re forecasting for the weekend the low 80s, which is a few degrees above normal, mostly dry conditions,” Adams said. “And then it’ll get a bit hotter Monday and Tuesday. So we’ll be about 10 degrees above normal Monday, Tuesday and Wednesday.”
The average high temperature for Boise in late September is around 76 degrees.
How does this affect Boise fall foliage?
The Farmers’ Almanac and Smoky Mountains, a Tennessee-based company specializing in vacation experiences in national parks, predict that fall foliage will be at its peak in the Treasure Valley in early-to-mid October.
But the amount of moisture in the air and soil could move that timeline somewhat.
“When it is drier sometimes that fall foliage, the turning of the leaves, can happen a little bit sooner,” Adams said.
The storms that passed through the Treasure Valley on Wednesday dropped 0.07 inches of rain — enough to wet the soil but not enough to cause any significant change.
Adams expects that fall foliage will peak in the Treasure Valley around early October because of the high-level ridge keeping the skies dry and clear.
The interactive map below shows when fall foliage typically peaks in your county, using data from the National Oceanic and Atmospheric Administration, including historical and forecasted temperature and precipitation, historical leaf peak trends and user reports.
