Allentown, PA

Pennsylvania · Records since 1922–2026

☀️ 80°F
Currently in Allentown
As of 2:30 PM EDT

Records for September 11

🔥 Record High

96°F

September 11, 1983

+17° from 79° normal

❄ Record Low

39°F

September 11, 1995

-18° from 57° normal
🌞 Normal high: 79°F 🌑 Normal low: 57°F 1991–2020 normals

All-Time Records — Allentown

🔥
105°F
Hottest Day Ever
Jul 3, 1966
❄
-15°F
Coldest Day Ever
Jan 21, 1994
🌧
8.71"
Wettest Day Ever
Oct 8, 2005
☃
30.2"
Most Snow in One Day
Jan 23, 2016

First & Last Dates — Allentown

How early and how late each seasonal turning point has ever arrived, across the full period of record

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Range ever recorded Normal date (1991–2020)
215 days
Longest growing season
1977
138 days
Shortest growing season
1947
175 days
Normal growing season
1991–2020 average

Top 10 Record Highs — September 11

# Temp Date
🏆 96°F September 11, 1983
2 95°F September 11, 1964
3 95°F September 11, 1931
4 93°F September 11, 2013
5 91°F September 11, 2019
6 89°F September 11, 1961
7 88°F September 11, 1952
8 88°F September 11, 1925
9 86°F September 11, 1989
10 86°F September 11, 1947

Top 5 Record Lows — September 11

# Temp Date
🥶 39°F September 11, 1995
2 41°F September 11, 1967
3 41°F September 11, 1932
4 42°F September 11, 1924
5 44°F September 11, 1969
About this data — Records are sourced from the NOAA Threadex dataset via RCC ACIS, a quality-controlled record for long-term climate stations. Threadex adjusts for station relocations and observation-time changes, making records comparable across all years since 1922–2026. Climate normals represent the 1991–2020 average.

Heat Wave Summary — Allentown

threshold: 91°F (90th percentile of historical Jun–Aug highs)
4.3
Avg heat wave length
days (historical)
96°
Avg peak temp
during heat waves
12
Dangerous nights 2026
Overnights ≥ 70°F
1
Heat waves 2026
so far

Days ≥ 90°F Per Year

1922–2026
17
2026 so far
17
Avg/year 1970–2025
23
Avg/year (last 10 complete)
41
Most in a year (1966)

Average Daily High by Decade

Full year · complete decades only

Longest Heat Waves — Allentown

# Dates Days Peak Avg High Avg Overnight Low
🏆 Jun 18, 1923 – Jun 26, 1923 9 100°F (Jun 20) 96°F 68°F
2 Jul 15, 1955 – Jul 23, 1955 9 100°F (Jul 22) 95°F 67°F
3 Jul 28, 2002 – Aug 5, 2002 9 99°F (Aug 2) 94°F 69°F
4 Aug 11, 2002 – Aug 19, 2002 9 99°F (Aug 14) 95°F 67°F
5 Jun 20, 1943 – Jun 28, 1943 9 98°F (Jun 26) 94°F 68°F
6 Jul 17, 2011 – Jul 24, 2011 8 104°F (Jul 22) 96°F 71°F
7 Aug 27, 1953 – Sep 3, 1953 8 99°F (Aug 31) 97°F 66°F
8 Aug 2, 1930 – Aug 9, 1930 8 98°F (Aug 4) 94°F 67°F
9 Aug 10, 1944 – Aug 17, 1944 8 98°F (Aug 12) 96°F 68°F
10 Aug 28, 1973 – Sep 4, 1973 8 97°F (Aug 28) 94°F 69°F

Heat Waves Per Year

Warm Summer Nights (Jun–Aug)

Nights where the overnight low exceeded the 1991–2020 normal low

43
2026 total
above-normal nights
42.6
Avg / summer
1970–2020
59
Most in a summer
1994

Above-Normal Summer Nights Per Year

Average June–August Low by Decade

Overnight lows · complete decades only

Precipitation

Annual totals and trend across the full period of record · see this year's standing →

Monthly Precipitation — Last 24 Months

Blue = actual · dashed line = monthly normal

Annual Precipitation Per Year (1912–2026)

Blue = above average · tan = below average · gold = 2026 (partial)
Since 1912, annual totals have trended +0.66" per decade, about +7.4" across the record.

Heavy Rain Days Per Year (≥ 1.0")

Compare year-to-year changes in days with heavy rainfall (≥ 1.0")

This Year — 2026

How Allentown is tracking against normal, year to date

Daily High Temperature vs Normal

Above normal Below normal

98 of 253 days with data were above the 1991–2020 normal high for their date.

Precipitation, Year to Date

27.01"
2026 YTD
Normal: 32.74"
-5.73"
1.49"
September so far
September normal: 4.84"
-3.35"
5
2026 heavy rain days
Days with ≥ 1.0"

Accumulation vs. Normal

Running total since Jan 1 against the normal pace for the same date · Allentown is 5.73" behind the normal pace

Period Review — Sep 1 – Sep 10, 2026

Any window, evaluated against every other year on record — 10 days

Quick picks: Last 7 days Last 30 days Last 90 days This month
Seasons: Spring (Mar–May) Summer (Jun–Aug) Fall (Sep–Nov)
72.4°F
Average temperature
20th-warmest of 103
+3.0°
vs. average
Normal: 69.4°F (1991–2020)
1.49"
Precipitation
40th-wettest of 111
+0.21"
vs. average
Normal: 1.28" · 116% of normal

Average Temperature by Year — Sep 1 – Sep 10

1923–2026 · 2026 highlighted

Precipitation by Year — Sep 1 – Sep 10

1912–2026 · 2026 highlighted · trend +0.03" per decade (wetter since 1912)

Warmest Sep 1 – Sep 10 on Record

# Year Avg Temp
1 1961 77.6°F
2 2015 76.5°F
3 1929 76.3°F
4 1980 75.8°F
5 1985 75.3°F
6 1959 75.3°F
7 2016 75.3°F
8 1983 74.8°F
9 2023 74.1°F
10 1947 74.0°F

Coolest Sep 1 – Sep 10 on Record

# Year Avg Temp
1 2017 62.3°F
2 1935 62.6°F
3 1986 62.6°F
4 1988 63.1°F
5 2024 63.3°F
6 1949 63.5°F
7 1967 63.6°F
8 1975 63.8°F
9 1994 63.8°F
10 1962 64.3°F

Wettest Sep 1 – Sep 10 on Record

# Year Total
1 2011 7.14"
2 1987 6.12"
3 2021 5.93"
4 1952 4.99"
5 1935 4.91"
6 1934 4.46"
7 1929 3.40"
8 1953 3.28"
9 2017 3.17"
10 1979 3.06"

Driest Sep 1 – Sep 10 on Record

# Year Total
1 2010 0.00"
2 2005 0.00"
3 1989 0.00"
4 1983 0.00"
5 1971 0.00"
6 1964 0.00"
7 1955 0.00"
8 1943 0.00"
9 1918 0.00"
10 2009 0.03"
About this data. Pick any start and end date and this becomes the same kind of review as the Month and Fall tabs, just for exactly the window you asked for — the generalized version of the same engine, evaluated across every year on record. Average temperature is the mean of each day's (high + low) / 2; precipitation is the sum of daily totals. A year missing more than about a fifth of the window's days is excluded from the temperature ranking; any missing day excludes a year from the precipitation ranking, since an unreported day is unreported rain. Ranges that cross from December into January aren't supported yet. Normals are the 1991–2020 mean for the same window.
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