Valentine’s Day offers a distraction from dreary Pacific Northwest winter weather and actually signals a beginning of the end of winter in the Boise Valley.
Southwestern Idaho’s winter climate is affected by the Pacific Ocean, which protects Idaho from the frigid conditions typical of the plains states. But the ocean also contributes cloud cover that causes this area to have fewer hours of sunshine on winter days than most locations in the continental U.S.
Another factor making Boise Valley’s winter weather unusual is atmospheric high pressure that tends to build over Utah and Idaho in the winter months. This well-documented phenomenon shields our area from storms. While other locations are lashed by a succession of winter storms, Idaho and Utah are often dry and relatively breeze-free during most of December and January. If the weather is favorable, we may see weeks of clear sunny weather, as has been the case this winter. Otherwise, we may be trapped for weeks under a cloud of fog, smog and exhaust fumes when a temperature inversion develops. So the Utah-Idaho high pressure system may be our friend or foe from year to year, but it nearly always causes us to have weeks of rather unchanging winter weather.
As Valentine’s Day draws near on the calendar, the  winter’s atmospheric high pressure system begins to break down. More storms blast their way into Idaho, causing unsettled conditions but also a much-desired end to persistent temperature inversions. From this time on, weather events tend to last only a few days before a change occurs.
Of course the daylight hours are increasing also: from 8 hours and 58 minutes of daylight on December 14 to 9 hours and 17 minutes on January 14 to 10 hours and 29 minutes on February 14. The average high temperature also rebounds from January’s nadir of 35 degrees to reach 44 degrees around Valentine’s Day. Wintry weather will remain in the Boise area for weeks after Valentine’s Day but the monotony should fade.

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