Weather on December 21
Boise, ID
55 Years of Data
Avg High
38°F
Avg Low
25°F
Warmest
2020
50°F avg
Coldest
1990
-13°F avg
About This Date
December 21st in Boise, ID typically brings cold winter weather, with average highs around 38°F and lows near 25°F. Over 55 years of records, the warmest December 21st was in 2020 (50°F average), while the coldest was 1990 (-13°F) — a 63°F range across recorded history. Precipitation has occurred on 45% of recorded December 21st dates, with snow falling 15% of the time (heaviest snowfall: 3.1"). The last decade has been 4.9°F warmer on this date compared to 20-30 years ago.
The last decade has been 4.9°F warmer on this date compared to 20-30 years ago.
Planning for December 21st in Boise, ID? Bundle up with warm layers and protect extremities from the cold. Consider bringing rain gear or an umbrella.
Warming Trend
1.1°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 45° | 36° | 40° | 2.36" | — |
| 2024 | 41° | 32° | 37° | 0.03" | — |
| 2023 | 37° | 32° | 35° | 0.03" | — |
| 2022 | 38° | 17° | 28° | 0.03" | — |
| 2021 | 42° | 25° | 34° | — | — |
| 2020warmest | 58° | 43° | 50° | — | — |
| 2019 | 50° | 40° | 45° | — | — |
| 2018 | 41° | 29° | 35° | 0.03" | — |
| 2017 | 35° | 22° | 29° | — | — |
| 2016 | 30° | 11° | 21° | — | — |
| 2015 | 45° | 34° | 39° | 0.28" | — |
| 2014 | 47° | 40° | 43° | 1.93" | — |
| 2013 | 30° | 21° | 26° | 0.05" | 0.2" |
| 2012 | 46° | 39° | 43° | — | — |
| 2011 | 42° | 18° | 30° | — | — |
| 2010 | 42° | 28° | 35° | — | — |
| 2009 | 48° | 34° | 41° | 0.03" | — |
| 2008 | 36° | 24° | 30° | 0.28" | 2.5" |
| 2007 | 35° | 22° | 28° | — | — |
| 2006 | 28° | 19° | 24° | 0.23" | 0.9" |
| 2005 | 49° | 32° | 40° | 0.71" | — |
| 2004 | 36° | 20° | 28° | — | — |
| 2003 | 45° | 30° | 37° | 0.05" | — |
| 2002 | 42° | 33° | 38° | 0.28" | — |
| 2001 | 36° | 25° | 30° | — | — |
| 2000 | 44° | 29° | 36° | — | — |
| 1999 | 47° | 25° | 36° | — | — |
| 1998 | 13° | -2° | 5° | — | — |
| 1997 | 37° | 22° | 29° | — | — |
| 1996 | 35° | 18° | 26° | 0.05" | 0.3" |
| 1995 | 36° | 24° | 30° | — | — |
| 1994 | 37° | 26° | 32° | — | — |
| 1993 | 31° | 26° | 28° | — | — |
| 1992 | 36° | 31° | 33° | — | — |
| 1991 | 34° | 17° | 25° | — | — |
| 1990coldest | -3° | -23° | -13° | 0.03" | 0.1" |
| 1989 | 46° | 17° | 32° | — | — |
| 1988 | 39° | 29° | 34° | 0.58" | 3.1" |
| 1987 | 42° | 31° | 36° | — | — |
| 1986 | 27° | 21° | 24° | — | — |
| 1985 | 13° | -3° | 5° | — | — |
| 1984 | 16° | -1° | 8° | 0.1" | 0.3" |
| 1983 | 14° | -8° | 3° | 0.03" | — |
| 1982 | 52° | 41° | 46° | 0.08" | — |
| 1981 | 45° | 32° | 38° | 0.84" | — |
| 1980 | 47° | 27° | 37° | 0.23" | — |
| 1979 | 46° | 36° | 41° | 0.43" | — |
| 1978 | 41° | 29° | 35° | 0.05" | 0.2" |
| 1977 | 35° | 23° | 29° | — | — |
| 1976 | 35° | 8° | 22° | — | — |
| 1975 | 21° | 17° | 19° | — | — |
| 1974 | 53° | 32° | 43° | — | — |
| 1973 | 48° | 38° | 43° | 0.33" | — |
| 1972 | 51° | 46° | 49° | — | — |
| 1971 | 44° | 37° | 41° | — | — |
55 years of data from BOISE AIR TERMINAL