Colorado · county records since 1895, through September 2026.
Weather › Colorado › Boulder County
Boulder County just had its warmest September ever recorded, +4° against the usual. Boulder County is in extreme drought: NOAA's Palmer reading for September was -7.9.
That is the 1991 to 2020 average for these dates in Boulder County. The Weather Service forecast fills in below.
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Each bar is a month's average temperature against the usual for that month (1991 to 2020). Ranks compare the same month in every year since 1895.
Rain and melted snow against the usual for each month. The drought reading is NOAA's Palmer index for the county.
| Month | Usual high / low | Usual rain | Warmest | Coldest |
|---|---|---|---|---|
| January | 40° / 17° | 1.0 in | 34.4° 1986 | 12.0° 1930 |
| February | 41° / 17° | 1.1 in | 37.2° 1954 | 12.8° 1899 |
| March | 49° / 23° | 1.9 in | 46.0° 2026 | 22.6° 1924 |
| April | 55° / 29° | 2.8 in | 47.8° 1981 | 32.6° 1920 |
| May | 64° / 38° | 2.8 in | 56.9° 1934 | 42.6° 1917 |
| June | 75° / 46° | 1.8 in | 65.6° 2012 | 53.5° 1951 |
| July | 81° / 52° | 2.1 in | 70.2° 2003 | 59.2° 1895 |
| August | 79° / 50° | 1.9 in | 67.9° 2026 | 58.8° 1927 |
| September | 71° / 43° | 1.6 in | 61.1° 2026 | 49.0° 1912 |
| October | 59° / 32° | 1.4 in | 51.6° 1963 | 36.3° 1969 |
| November | 47° / 24° | 1.2 in | 42.8° 1949 | 25.0° 1929 |
| December | 39° / 16° | 0.9 in | 37.2° 1980 | 16.6° 1909 |
Warmest and coldest are the month's whole-month average temperature, with the year it happened.