March 2016 was the 7th warmest at the airport, where records go back to 1940. It was a month of changeable and sometimes extreme weather typical of early spring.
From the 1st through the 13th the temperature averaged 8 degrees above normal. This was primarily due to persistent relatively warm southwest flow aloft. Disturbances embedded in the flow weakened as they moved inland, but they carried enough moisture to bring showers to Boise nearly every day.
The pattern changed at mid-month. Northwest flow aloft followed the passage of an upper level trough on the 14th, keeping temperatures below normal through the 18th. The low of 28°F on the 18th was the first freezing temperature since February 25th.
On the 19th an upper level ridge made a brief sojourn over the Intermountain region and temperatures were again above normal.
After the ridge departed to the east, southwest flow aloft ahead of a Gulf of Alaska trough kept temperatures above normal through the 21st. The 70°F on the 20th, The First Day of Spring, was the high for the month and the first 70°F since October 25th.
As the trough drew closer on the evening of the 21st, strong thunderstorms developed along the cold front, dumping over a third of an inch of rain at the Boise Airport. Two to three times that fell at other locations around town, along with hail up to grape size which covered the ground in some places.
That trough paved the way for two more Gulf of Alaska troughs.
A second trough arrived on the 25th, ushered in by chilly northwest winds gusting to 43 mph at the airport. In contrast to the trough, four days earlier, there was only a trace of rain. The winds subsided that evening and skies cleared, allowing the temperature to fall to 27°F after a week of above-freezing lows.
The third and deepest trough arrived on the 28th. The coldest air was already over Boise early that morning, reflected by a low of 28°F. By evening the upper level low center and coldest air had settled over the Great Basin and California.
By the morning of the 29th a deep surface low had formed, centered near the Utah-Colorado border. By afternoon it had developed into a major spring snowstorm for the Magic Valley and southeast Idaho.
Boise, being too far north and west to see any precipitation, experienced only dry northwest winds, with gusts in the 20 to 30 mph range at the airport. In contrast to the cold wet weather farther east, the temperature at the airport reached 60°F that afternoon.
Under mostly clear skies temperatures continued to warm on the 30th and 31st in response to a high pressure ridge which extended from the California coast all the way to Alaska.