The National Weather Service has issued a winter weather advisory for the upper Treasure Valley from 2 a.m. to 11 a.m. Thursday, so morning commuters should be prepared for snow on the roads. Forecasters expect up to 2 inches of snow will fall by noon.

But there is some good news: High temperatures Thursday may rise to the upper-20s — practically a heat wave after days of frigid weather. Wednesday's high was 20.

It’s been 12 straight days since Boise has gotten above 32 degrees.

A weather system expected to move through the Treasure Valley Wednesday night should to push some of the frigid, filthy air that has been parked over Boise for the last few weeks. But don't get too excited. The Idaho Department of Environmental Quality has issued a yellow air quality alert for Thursday, meaning air quality might continue to be a problem for the most sensitive individuals.

Friday is expected to be hazy and sunny but Treasure Valley residents should expect snow over the weekend as another storm system moves through. Beginning Thursday, high temperatures for the next several days are expected to be in the low to mid 30s, with lows in the 20s, according to National Weather Service reports.

Treasure Valleyans have now endured three solid weeks of frigid temperatures. All but two days in January have been below normal — and not just a little. We're talking average daily temperatures that have been 10 to 24 degrees below normal.

For example, the high temperature in Boise on Tuesday was 19 degrees. The high on Jan. 22, 2012 was 41 degrees. The average high temperature for Jan. 21 is 38 degrees.

The average temperature for January to-date is 15.4. That ties the second coldest January since 1865 (1937 was the other second coldest). The coldest January was 1949, when the average monthly temperature was 10.3.