July was hot. The average temperature of 81.6 degrees ranked the second warmest month for all years back to 1877. Only July 2007, which averaged 83.1 degrees, was hotter. On the other end of the scale, July 1993 averaged a rather chilly 65.0 degrees.
It was a dry month. Only 0.01 inch was measured at the airport. Dry summer months are not unusual. Since 1877, 33 July’s were as dry or drier.
A semi-permanent warm upper level ridge, which normally forms over the Colorado Plateau during late spring and early summer, kept most of the Northwest U. S. dry through the month. Weather systems from the Gulf of Alaska were blocked from penetrating very far south of the Canadian border, and were forced to move east over southern Canada.
On three occasions the ridge expanded north. From the 4th through the 9th, the 13th through the 15th, and the 29th through the 31st, Boise was directly under the ridge, resulting in triple digit highs.
Monsoon moisture drifting north from Nevada produced locally wet late afternoon and evening thunderstorms. On several days, thunderstorms formed over Owyhee County, but they weakened as they moved over the Owyhee Mountains. Any rain that reached the ground usually missed the National Weather Service rain gauges.
