Weather on September 21
Allentown, PA
55 Years of Data
Avg High
75°F
Avg Low
53°F
Warmest
1980
78°F avg
Coldest
2020
50°F avg
About This Date
September 21st in Allentown, PA typically brings pleasant fall weather, with average highs around 75°F and lows near 53°F. Over 55 years of records, the warmest September 21st was in 1980 (78°F average), while the coldest was 2020 (50°F) — a 28°F range across recorded history. Rain or other precipitation has occurred on about 33% of September 21st dates historically, with the wettest September 21st recording 8.15" of rain. The last decade has been 2.3°F warmer on this date compared to 20-30 years ago.
The last decade has been 2.3°F warmer on this date compared to 20-30 years ago.
Planning for September 21st in Allentown, PA? Great weather for outdoor activities. Consider bringing rain gear or an umbrella.
Warming Trend
0.7°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 73° | 50° | 62° | — | — |
| 2024 | 79° | 62° | 70° | — | — |
| 2023 | 74° | 47° | 60° | — | — |
| 2022 | 80° | 55° | 68° | — | — |
| 2021 | 78° | 54° | 66° | — | — |
| 2020coldest | 66° | 33° | 50° | — | — |
| 2019 | 87° | 50° | 69° | — | — |
| 2018 | 74° | 65° | 69° | 0.03" | — |
| 2017 | 88° | 61° | 74° | — | — |
| 2016 | 86° | 59° | 73° | — | — |
| 2015 | 70° | 52° | 61° | — | — |
| 2014 | 81° | 54° | 67° | 0.1" | — |
| 2013 | 78° | 52° | 65° | 1.73" | — |
| 2012 | 76° | 51° | 63° | — | — |
| 2011 | 74° | 60° | 67° | 0.43" | — |
| 2010 | 76° | 40° | 58° | — | — |
| 2009 | 75° | 47° | 61° | — | — |
| 2008 | 81° | 44° | 62° | — | — |
| 2007 | 84° | 53° | 69° | — | — |
| 2006 | 67° | 41° | 54° | — | — |
| 2005 | 84° | 56° | 70° | — | — |
| 2004 | 81° | 49° | 65° | — | — |
| 2003 | 75° | 51° | 63° | — | — |
| 2002 | 82° | 67° | 74° | 0.36" | — |
| 2001 | 80° | 57° | 69° | 0.03" | — |
| 2000 | 72° | 47° | 59° | — | — |
| 1999 | 63° | 50° | 56° | 0.89" | — |
| 1998 | 82° | 60° | 71° | 0.05" | — |
| 1997 | 61° | 42° | 51° | — | — |
| 1996 | 76° | 45° | 60° | — | — |
| 1995 | 81° | 63° | 72° | — | — |
| 1994 | 80° | 49° | 64° | — | — |
| 1993 | 61° | 53° | 57° | 0.18" | — |
| 1992 | 75° | 57° | 66° | — | — |
| 1991 | 63° | 43° | 53° | — | — |
| 1990 | 70° | 43° | 56° | — | — |
| 1989 | 84° | 71° | 78° | 1.24" | — |
| 1988 | 72° | 61° | 66° | — | — |
| 1987 | 72° | 58° | 65° | 0.18" | — |
| 1986 | 74° | 59° | 66° | — | — |
| 1985 | 80° | 54° | 67° | — | — |
| 1984 | 77° | 54° | 65° | — | — |
| 1983 | 76° | 55° | 65° | 2.39" | — |
| 1982 | 67° | 55° | 61° | — | — |
| 1981 | 67° | 43° | 55° | — | — |
| 1980warmest | 89° | 67° | 78° | — | — |
| 1979 | 65° | 52° | 58° | 8.15" | — |
| 1978 | 84° | 61° | 72° | — | — |
| 1977 | 66° | 55° | 61° | 0.18" | — |
| 1976 | 69° | 49° | 59° | — | — |
| 1975 | 72° | 57° | 64° | 0.05" | — |
| 1974 | 77° | 51° | 64° | 0.51" | — |
| 1973 | 64° | 42° | 53° | — | — |
| 1972 | 61° | 51° | 56° | 0.05" | — |
| 1971 | 72° | 50° | 61° | 0.66" | — |
55 years of data from ALLENTOWN LEHIGH VLY INTL AP