Unseasonably cool weather at the end of the month compensated for hot weather at the beginning and middle of the month, so the average temperature was exactly normal. Total precipitation was a quarter inch above normal.
It was wet nearly everywhere, with parts of Malheur County getting over three times normal precipitation.
Summer weather persisted through the first week of September, with a strong upper level high pressure ridge anchored over the western half of the nation.
A record high of 101 was set at Ontario on the 5th.
The 99 degrees on the 5th was the culmination of a streak of 9 consecutive days with highs over 90.
Airflow from the Desert Southwest brought enough monsoon moisture for isolated thunderstorms on the 5th and 6th. On the 6th, 0.15 inch of rain fell, exceeding our total summer rainfall by a hundredth of an inch.
Thunderstorms on the 5th was preceded by gusts over 55 mph near Swan Falls, in the Boise area, and at Glenns Ferry. In Boise, a microburst knocked down numerous trees from Broadway to Apple Street, some falling on houses. At Timberline High School fences were knocked down, and a batting cage was lifted over a baseball field fence and thrown into an adjacent parking lot.
Southeast Boise got hit hard by Thursday night's storm including significant damage at Timberline High's tennis courts. https://t.co/4sELuNnrTl
— CBS 2 News (@CBS2Boise) September 6, 2019
On the 6th large tree branches were blown down near Buhl and at Glenns Ferry.
If you experienced chaotic weather the past few days, you weren't alone! Here's a map of all of the cloud-to-ground #lightning strikes detected in the past 72 hours across the region! There are around 19,400 strikes on this map. #IDwx #ORwx pic.twitter.com/RJOcWJVNw5
— NWS Boise (@NWSBoise) September 8, 2019
On the 8th a Pacific cold front dropped a third of an inch of rain at Boise. The .52 inch total at Mountain Home AFB set a record for the date.
On the 9th one-inch diameter hail fell at several locations near Twin Falls and Eden in Jerome County. Near Hansen in Twin Falls County 1.5 inch diameter hail was reported.
The upper level trough following the front kept temperatures a few degrees below normal through the 11th.
After the trough exited on the 12th, warm dry air south of the jet stream raised temperatures above normal. In the Treasure Valley the last 90-degree highs of the summer were recorded on the 14th and 15th. The 95 at Ontario on the 15th tied the record for the date set in 1956.
On the 16th an upper level trough from the Gulf of Alaska, followed by a second trough on the 19th, maintained cool showery weather through the 21st.
After the trough departed, temperatures were slightly above normal from the 22nd through the 27th.
During the early morning hours of the 28th, a strong cold front imported much cooler air from Alaska as a major upper level trough deepened over the northwest U.S. Temperatures averaged nearly 15 degrees below normal for the final three days of the month.
At Burns on the 30th the low of 23 tied the record set in 1981.