Weather on August 21
Naperville, IL
55 Years of Data
Avg High
83°F
Avg Low
60°F
Warmest
2003
85°F avg
Coldest
2012
62°F avg
About This Date
August 21st in Naperville, IL typically brings warm summer weather, with average highs around 83°F and lows near 60°F. Over 54 years of records, the warmest August 21st was in 2003 (85°F average), while the coldest was 2012 (62°F) — a 23°F range across recorded history. Rain or other precipitation has occurred on about 33% of August 21st dates historically, with the wettest August 21st recording 3.58" of rain. The last decade has been 1.1°F cooler on this date compared to 20-30 years ago.
The last decade has been 1.1°F cooler on this date compared to 20-30 years ago.
Planning for August 21st in Naperville, IL? Stay hydrated and seek shade during peak afternoon hours. Consider bringing rain gear or an umbrella.
Cooling Trend
0.8°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 78° | 61° | 69° | — | — |
| 2024 | 77° | 49° | 63° | — | — |
| 2023 | 90° | 64° | 77° | — | — |
| 2022 | 75° | 62° | 69° | 0.36" | — |
| 2021 | 90° | 67° | 78° | — | — |
| 2020 | 83° | 57° | 70° | — | — |
| 2019 | 75° | 61° | 68° | 0.43" | — |
| 2018 | 77° | 67° | 72° | 3.28" | — |
| 2017 | 88° | 58° | 73° | 0.76" | — |
| 2016 | 74° | 58° | 66° | 1.91" | — |
| 2015 | 74° | 53° | 63° | — | — |
| 2014 | 85° | 65° | 75° | 3.58" | — |
| 2013 | 87° | 61° | 74° | — | — |
| 2012coldest | 76° | 49° | 62° | 0.3" | — |
| 2011 | 80° | 64° | 72° | 1.32" | — |
| 2010 | 92° | 65° | 78° | 3.3" | — |
| 2009 | 72° | 55° | 63° | 0.43" | — |
| 2008 | 81° | 60° | 70° | — | — |
| 2007 | 76° | 69° | 72° | 0.66" | — |
| 2006 | 82° | 52° | 67° | — | — |
| 2005 | 81° | 58° | 69° | 0.08" | — |
| 2004 | 75° | 53° | 64° | — | — |
| 2003warmest | 95° | 75° | 85° | — | — |
| 2002 | 88° | 58° | 73° | — | — |
| 2001 | 82° | 54° | 68° | — | — |
| 2000 | 82° | 56° | 69° | — | — |
| 1999 | 81° | 51° | 66° | — | — |
| 1998 | 92° | 69° | 80° | — | — |
| 1997 | 74° | 55° | 64° | — | — |
| 1996 | 88° | 69° | 78° | 1.52" | — |
| 1995 | 90° | 61° | 75° | — | — |
| 1994 | 77° | 61° | 69° | 0.15" | — |
| 1993 | 83° | 64° | 73° | — | — |
| 1992 | 81° | 47° | 64° | — | — |
| 1991 | 85° | 51° | 68° | — | — |
| 1990 | 73° | 66° | 70° | 1.83" | — |
| 1989 | 87° | 59° | 73° | — | — |
| 1988 | 82° | 66° | 74° | — | — |
| 1987 | 85° | 66° | 75° | 1.4" | — |
| 1985 | 76° | 50° | 63° | — | — |
| 1984 | 86° | 56° | 71° | — | — |
| 1983 | 96° | 67° | 81° | — | — |
| 1982 | 85° | 55° | 70° | — | — |
| 1981 | 84° | 49° | 66° | — | — |
| 1980 | 93° | 69° | 81° | 2.51" | — |
| 1979 | 80° | 67° | 73° | — | — |
| 1978 | 81° | 52° | 66° | — | — |
| 1977 | 75° | 58° | 66° | 0.13" | — |
| 1976 | 86° | 55° | 71° | — | — |
| 1975 | 94° | 68° | 81° | — | — |
| 1974 | 89° | 65° | 77° | — | — |
| 1973 | 84° | 53° | 69° | — | — |
| 1972 | 89° | 71° | 80° | — | — |
| 1971 | 93° | 64° | 79° | — | — |
54 years of data from LISLE - MORTON ARBORETUM