August 2015 Climate Summary for Boise


August mean temperature of 77.4°F was warmer than July (76.6°F), which happens about one of every four years. The temperature reached 100°F five times in August, with two record highs set on Aug 11 and Aug 13 (106°F).  It may have been warmer, but most of the area was plagued by smoke from wildfires.  Smoke retards daytime heating by scattering sunlight but has no effect on overnight temperatures.

Precipitation was close to normal.

The month started out very hot with a high pressure ridge covering most of the western and southern states south of the Canadian border.  On the 1st and 2nd temperatures soared into the triple digits for the first time since July 4 at Boise.  A few cooler days followed as low pressure systems from the Gulf of Alaska attempted to dislodge the ridge.  By the 11th the ridge had regained control sending temperatures back up to the triple digits in the lower valleys.  The ridge maintained its strength through the 14th.  But by the 15th it had retreated south and east allowing northwest flow to bring a temporary respite from the above normal temperatures.  On the 23rd the ridge had returned for a week-long encore, but the heat was less intense than earlier in the month.  A low pressure trough which had stalled offshore swung inland bringing measurable rain to northern Idaho and northeast Oregon by the 30th.