Boise September Weather

Averages and records for weather in Boise, Idaho in the month of September.
Typical Boise September Weather
1991–2020
Average daily high 80.0 °F
Average daily low 52.1 °F
Average monthly precipitation 0.4 inches
Average monthly snow none
Boise September Weather Records
1911–2023
Highest temperature 105 °F September 4, 1924
Lowest temperature 22 °F September 24, 1926
Highest daily low 76 °F September 5, 1998
Lowest daily high 48 °F September 30, 1971
Hottest average temperature 5.6 °F
above average
2011
Coldest average temperature -9.7 °F
below average
1921
Most daily precipitation 1.7 inches September 11, 1976
Most monthly precipitation 2.9 inches 1986
Most daily snow none -
Most monthly snow none -
Note: Daily averages are a moving average which includes 14 days before and after
Day Average (°F) Record (°F)
High Low High Low
September 1 85.8 56.5 102 36
September 2 85.4 56.3 101 38
September 3 84.9 56.0 102 37
September 4 84.4 55.7 105 36
September 5 83.9 55.3 100 36
September 6 83.5 55.0 101 37
September 7 83.1 54.6 104 31
September 8 82.7 54.3 95 29
September 9 82.3 54.0 98 33
September 10 81.9 53.7 97 34
September 11 81.5 53.4 97 30
September 12 81.1 53.1 94 32
September 13 80.7 52.7 94 28
September 14 80.3 52.4 101 23
September 15 80.1 52.2 95 29
September 16 79.8 52.0 93 29
September 17 79.5 51.8 95 24
September 18 79.0 51.4 97 27
September 19 78.4 51.1 97 31
September 20 77.9 50.6 96 33
September 21 77.3 50.2 95 29
September 22 76.8 49.9 99 28
September 23 76.4 49.6 95 28
September 24 76.0 49.3 98 22
September 25 75.6 48.9 95 23
September 26 75.0 48.5 93 23
September 27 74.4 48.1 95 28
September 28 73.9 47.6 95 29
September 29 73.4 47.2 95 27
September 30 72.9 46.8 96 29
Weather Station Details
Years Station Coordinates
1940–2023 location
1911–1939 Meridian 1 W location