It was the second driest June at the Boise Airport, where records go back to 1940. It was the fourth driest June at all Boise locations going back to 1864. Measurable rain fell on only two days.
The average temperature for the month was very close to normal.
June began with above normal temperatures, with highs in the 80s under an upper level high pressure ridge.
On the 7th a pacific cold front, followed by an upper level low pressure trough, brought a brief break in the warm weather. Highs were only in the lower 60s on the 7th and 8th.
By the 10th temperatures had risen above normal again as another high pressure ridge began to build over the west coast. Highs were in the 80s from the 10th through the 19th, with the exception of the 91 on the 12th. That was the first 90 degree reading since September 7.
Following the 80 degrees on the 19th, much cooler air spread south following a cold front as an upper level trough deepened over southwest Canada and the northwest U.S. Highs were only in the mid 60s on the 20th and 21st.
After a chilly 42 degree low on the 22nd, temperatures began a slow recovery as the trough exited to the east. By the 25th milder west-southwest flow aloft had returned temperatures to near normal.
On the 26th an upper level trough from the Gulf of Alaska had arrived off the Washington-Oregon coast. Coming from the cold waters of the northeast Pacific, it contained little moisture.
Ahead of the trough, southwest flow aloft helped the temperature warm to 89 on the 26th.
As the trough edged further east that day, thunderstorms developed in northeast Oregon along a weak cold front. But they never got as far as Boise, and that night the front produced no precipitation as it crossed southwest Idaho.
The trough gradually weakened and moved offshore. It continued to have little effect on our area, although on the 28th a stationary band of dense high clouds prevented temperatures from rising above the lower 70s.
