December weather in Longmont, CO
The average temperature in Longmont in December is 29.6°F (14.5°F–44.8°F). Average precipitation: 0.46 inches.
December is a winter month in Longmont, and is cooler than the annual average of 50°F. Daily temperatures swing about 30.3°F between overnight low and afternoon high. Expect about 3 days with precipitation. Daylight averages about 9h 9m. For travel, December is cold.
Avg High
44.8°F
Avg Low
14.5°F
Precipitation
0.46 in
Daylight
9h 9m
December records in Longmont
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| December 1 | 70.0°F (1917) | -16.1°F (1929) | 0.69 in (1945) |
| December 2 | 75.9°F (2021) | -11.0°F (1919) | 0.74 in (1933) |
| December 3 | 75.0°F (1941) | 0.0°F (1919) | 0.36 in (2025) |
| December 4 | 75.0°F (1939) | -11.0°F (1955) | 2.45 in (1913) |
| December 5 | 70.0°F (1980) | -17.0°F (1909) | 0.74 in (1913) |
| December 6 | 77.0°F (1939) | -27.0°F (1972) | 0.37 in (1978) |
| December 7 | 68.0°F (1923) | -20.0°F (1972) | 0.19 in (1926) |
| December 8 | 70.0°F (1939) | -29.9°F (1919) | 0.56 in (1985) |
| December 9 | 71.1°F (1933) | -25.1°F (1919) | 0.56 in (1985) |
| December 10 | 69.1°F (1957) | -22.0°F (1972) | 0.24 in (1989) |
| December 11 | 78.1°F (1939) | -29.0°F (1932) | 0.19 in (2000) |
| December 12 | 71.1°F (1921) | -18.9°F (1932) | 0.25 in (1958) |
| December 13 | 73.9°F (1921) | -20.0°F (1926) | 0.85 in (1925) |
| December 14 | 73.0°F (1924) | -22.0°F (1926) | 0.29 in (1951) |
| December 15 | 70.0°F (1939) | -13.0°F (1972) | 0.44 in (1988) |
| December 16 | 66.9°F (1942) | -11.0°F (1972) | 0.20 in (1909) |
| December 17 | 71.1°F (1939) | -13.0°F (1964) | 0.20 in (1956) |
| December 18 | 70.0°F (1980) | -18.9°F (1924) | 0.11 in (1989) |
| December 19 | 70.0°F (1941) | -20.0°F (1924) | 0.55 in (1973) |
| December 20 | 72.0°F (2025) | -14.1°F (1913) | 0.22 in (1920) |
| December 21 | 66.0°F (1931) | -18.0°F (1990) | 0.34 in (1998) |
| December 22 | 71.1°F (1933) | -31.0°F (1990) | 0.51 in (1981) |
| December 23 | 77.0°F (2025) | -32.1°F (1924) | 0.30 in (1979) |
| December 24 | 73.0°F (1955) | -23.1°F (1989) | 0.72 in (1973) |
| December 25 | 71.1°F (1955) | -22.0°F (1989) | 0.68 in (1982) |
| December 26 | 70.0°F (2025) | -22.0°F (1989) | 0.65 in (1982) |
| December 27 | 70.0°F (1947) | -14.1°F (1988) | 0.45 in (1979) |
| December 28 | 66.9°F (1980) | -16.1°F (1988) | 0.58 in (1979) |
| December 29 | 64.0°F (1933) | -20.0°F (1983) | 1.23 in (2022) |
| December 30 | 69.1°F (1917) | -24.0°F (1923) | 0.22 in (1951) |
| December 31 | 72.0°F (1980) | -22.0°F (1918) | 0.15 in (1994) |