Weather on August 21
Boise, ID
55 Years of Data
Avg High
89°F
Avg Low
59°F
Warmest
2022
85°F avg
Coldest
1988
62°F avg
About This Date
August 21st in Boise, ID typically brings warm summer weather, with average highs around 89°F and lows near 59°F — a 30°F daily swing. Over 55 years of records, the warmest August 21st was in 2022 (85°F average), while the coldest was 1988 (62°F) — a 23°F range across recorded history. Rain or other precipitation has occurred on about 13% of August 21st dates historically, with the wettest August 21st recording 0.94" of rain. The last decade has been 2.0°F warmer on this date compared to 20-30 years ago.
The last decade has been 2.0°F warmer on this date compared to 20-30 years ago.
Planning for August 21st in Boise, ID? Stay hydrated and seek shade during peak afternoon hours.
Warming Trend
1.2°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 91° | 61° | 76° | — | — |
| 2024 | 88° | 61° | 74° | — | — |
| 2023 | 87° | 66° | 77° | 0.94" | — |
| 2022warmest | 100° | 69° | 85° | — | — |
| 2021 | 77° | 57° | 67° | 0.13" | — |
| 2020 | 92° | 66° | 79° | — | — |
| 2019 | 97° | 66° | 81° | — | — |
| 2018 | 81° | 55° | 68° | — | — |
| 2017 | 88° | 56° | 72° | — | — |
| 2016 | 95° | 63° | 79° | — | — |
| 2015 | 88° | 59° | 73° | — | — |
| 2014 | 83° | 58° | 70° | — | — |
| 2013 | 92° | 62° | 77° | — | — |
| 2012 | 94° | 72° | 83° | — | — |
| 2011 | 99° | 63° | 81° | — | — |
| 2010 | 94° | 63° | 78° | — | — |
| 2009 | 97° | 67° | 82° | — | — |
| 2008 | 83° | 61° | 72° | — | — |
| 2007 | 80° | 55° | 68° | — | — |
| 2006 | 100° | 65° | 82° | — | — |
| 2005 | 101° | 66° | 83° | — | — |
| 2004 | 94° | 67° | 80° | 0.03" | — |
| 2003 | 89° | 66° | 78° | 0.03" | — |
| 2002 | 75° | 54° | 64° | — | — |
| 2001 | 89° | 55° | 72° | — | — |
| 2000 | 83° | 49° | 66° | — | — |
| 1999 | 90° | 66° | 78° | — | — |
| 1998 | 90° | 58° | 74° | — | — |
| 1997 | 93° | 60° | 77° | — | — |
| 1996 | 82° | 50° | 66° | — | — |
| 1995 | 97° | 61° | 79° | — | — |
| 1994 | 89° | 54° | 71° | — | — |
| 1993 | 81° | 55° | 68° | — | — |
| 1992 | 96° | 62° | 79° | — | — |
| 1991 | 98° | 65° | 81° | — | — |
| 1990 | 80° | 53° | 67° | 0.03" | — |
| 1989 | 83° | 59° | 71° | — | — |
| 1988coldest | 81° | 44° | 62° | — | — |
| 1987 | 89° | 53° | 71° | — | — |
| 1986 | 84° | 62° | 73° | 0.08" | — |
| 1985 | 78° | 49° | 63° | — | — |
| 1984 | 90° | 52° | 71° | — | — |
| 1983 | 78° | 58° | 68° | — | — |
| 1982 | 94° | 58° | 76° | — | — |
| 1981 | 88° | 48° | 68° | — | — |
| 1980 | 88° | 50° | 69° | — | — |
| 1979 | 81° | 59° | 70° | 0.08" | — |
| 1978 | 87° | 47° | 67° | — | — |
| 1977 | 91° | 67° | 79° | — | — |
| 1976 | 96° | 55° | 76° | — | — |
| 1975 | 79° | 53° | 66° | — | — |
| 1974 | 87° | 53° | 70° | — | — |
| 1973 | 92° | 63° | 77° | — | — |
| 1972 | 89° | 56° | 72° | — | — |
| 1971 | 92° | 61° | 76° | — | — |
55 years of data from BOISE AIR TERMINAL