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Boulder September Weather

Averages and records for weather in Boulder, Colorado in the month of September.

Typical Boulder September Weather 1991–2020
Average daily high	78.7 °F
Average daily low	48.6 °F
Average monthly precipitation	2.1 inches
Average monthly snow	1.0 inches
Daily chance of precipitation	26.3%
Daily chance of snow	1.6%

Boulder September Weather Records 1893–2024
Highest temperature	100 °F	September 2, 2019
Lowest temperature	15 °F	September 30, 1985
Highest daily low	75 °F	September 3, 1947
Lowest daily high	35 °F	September 29, 1985
Hottest average high temperature	85.1 °F	1947
Coldest average high temperature	68.8 °F	1965
Most daily precipitation	9.1 inches	September 12, 2013
Most monthly precipitation	18.2 inches	2013
Most daily snow	18.0 inches	September 17, 1971
Most monthly snow	21.0 inches	1971

Note: Daily averages are a moving average which includes 14 days before and after

Day	Average (°F)		Record (°F)
Day	High	Low	High	Low
September 1	83.5	53.3	98	40
September 2	83.3	53.1	100	36
September 3	83.2	52.9	97	33
September 4	82.8	52.7	96	39
September 5	82.5	52.4	99	40
September 6	82.2	52.0	99	38
September 7	81.8	51.7	95	34
September 8	81.3	51.2	97	32
September 9	80.9	50.9	95	30
September 10	80.4	50.5	99	35
September 11	80.1	50.1	95	34
September 12	79.8	49.7	93	31
September 13	79.5	49.4	95	31
September 14	79.1	49.0	94	28
September 15	78.8	48.7	93	30
September 16	78.5	48.5	93	30
September 17	78.1	48.1	93	27
September 18	77.7	47.8	93	30
September 19	77.2	47.5	93	22
September 20	76.7	47.1	93	29
September 21	76.2	46.7	89	26
September 22	75.7	46.3	90	23
September 23	75.3	46.0	91	31
September 24	75.0	45.6	92	30
September 25	74.6	45.3	88	24
September 26	74.0	44.8	90	28
September 27	73.7	44.4	92	24
September 28	73.3	44.1	90	23
September 29	72.9	43.8	89	18
September 30	72.5	43.4	91	15

Weather Station Details

Years	Station	Coordinates
1893–2024	Boulder	location