Boston, MA

Massachusetts · Records since 1872–2026

☀️ 78°F Feels like 73°
Currently in Boston
As of 2:15 PM EDT

Records for September 11

🔥 Record High

99°F

September 11, 1983

+24° from 75° normal

❄ Record Low

40°F

September 11, 1917

-20° from 60° normal
🌞 Normal high: 75°F 🌑 Normal low: 60°F 1991–2020 normals

All-Time Records — Boston

🔥
104°F
Hottest Day Ever
Jul 4, 1911
❄
-18°F
Coldest Day Ever
Feb 9, 1934
🌧
7.06"
Wettest Day Ever
Aug 19, 1955
☃
23.6"
Most Snow in One Day
Jan 29, 2022

First & Last Dates — Boston

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)
254 days
Longest growing season
2009
162 days
Shortest growing season
1883
220 days
Normal growing season
1991–2020 average

Top 10 Record Highs — September 11

# Temp Date
🏆 99°F September 11, 1983
2 97°F September 11, 2013
3 95°F September 11, 1931
4 94°F September 11, 1961
5 90°F September 11, 1925
6 90°F September 11, 1912
7 90°F September 11, 1896
8 88°F September 11, 1915
9 88°F September 11, 1908
10 87°F September 11, 2019

Top 5 Record Lows — September 11

# Temp Date
🥶 40°F September 11, 1917
2 42°F September 11, 1875
3 44°F September 11, 1885
4 44°F September 11, 1883
5 45°F September 11, 1918
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 1872–2026. Climate normals represent the 1991–2020 average.

Heat Wave Summary — Boston

threshold: 90°F (90th percentile of historical Jun–Aug highs)
3.8
Avg heat wave length
days (historical)
96°
Avg peak temp
during heat waves
21
Dangerous nights 2026
Overnights ≥ 70°F
2
Heat waves 2026
so far

Days ≥ 90°F Per Year

1872–2026
16
2026 so far
12
Avg/year 1970–2025
17
Avg/year (last 10 complete)
30
Most in a year (1983)

Average Daily High by Decade

Full year · complete decades only

Longest Heat Waves — Boston

# Dates Days Peak Avg High Avg Overnight Low
🏆 Jul 3, 1912 – Jul 11, 1912 9 99°F (Jul 9) 93°F 70°F
2 Aug 10, 1944 – Aug 17, 1944 8 101°F (Aug 12) 97°F 73°F
3 Aug 11, 2002 – Aug 18, 2002 8 101°F (Aug 14) 95°F 74°F
4 Jun 28, 1872 – Jul 5, 1872 8 98°F (Jul 1) 94°F 70°F
5 Jul 19, 1994 – Jul 26, 1994 8 97°F (Jul 21) 92°F 72°F
6 Jul 19, 2022 – Jul 25, 2022 7 100°F (Jul 24) 94°F 74°F
7 Jul 15, 1983 – Jul 21, 1983 7 99°F (Jul 16) 94°F 72°F
8 Jul 14, 2013 – Jul 20, 2013 7 99°F (Jul 19) 94°F 75°F
9 Jun 27, 1901 – Jul 3, 1901 7 97°F (Jun 28) 94°F 73°F
10 Aug 9, 1988 – Aug 15, 1988 7 96°F (Aug 15) 93°F 73°F

Heat Waves Per Year

Warm Summer Nights (Jun–Aug)

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

62
2026 total
above-normal nights
40.3
Avg / summer
1970–2020
61
Most in a summer
1983

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 (1872–2026)

Blue = above average · tan = below average · gold = 2026 (partial)
Since 1872, annual totals have trended +0.10" per decade, about +1.6" 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 Boston is tracking against normal, year to date

Daily High Temperature vs Normal

Above normal Below normal

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

Precipitation, Year to Date

18.42"
2026 YTD
Normal: 29.10"
-10.68"
0.86"
September so far
September normal: 3.56"
-2.70"
3
2026 heavy rain days
Days with ≥ 1.0"

Accumulation vs. Normal

Running total since Jan 1 against the normal pace for the same date · Boston is 10.68" behind the normal pace

Period Review — Aug 11 – Sep 10, 2026

Any window, evaluated against every other year on record — 31 days

Quick picks: Last 7 days Last 30 days Last 90 days This month
Seasons: Spring (Mar–May) Summer (Jun–Aug) Fall (Sep–Nov)
72.2°F
Average temperature
21st-warmest of 155
+0.9°
vs. average
Normal: 71.3°F (1991–2020)
1.37"
Precipitation
17th-driest of 154
-1.82"
vs. average
Normal: 3.19" · 43% of normal

Average Temperature by Year — Aug 11 – Sep 10

1872–2026 · 2026 highlighted · trend +0.27° per decade (warming since 1872)

Precipitation by Year — Aug 11 – Sep 10

1872–2026 · 2026 highlighted · trend -0.04" per decade (drier since 1872)

Warmest Aug 11 – Sep 10 on Record

# Year Avg Temp
1 1959 76.2°F
2 2021 76.2°F
3 2016 75.0°F
4 2015 75.0°F
5 2018 74.9°F
6 1953 74.0°F
7 1983 73.8°F
8 1947 73.6°F
9 2002 73.5°F
10 1961 73.5°F

Coolest Aug 11 – Sep 10 on Record

# Year Avg Temp
1 1883 65.4°F
2 1885 65.5°F
3 1903 65.6°F
4 1934 65.8°F
5 1887 65.9°F
6 1890 66.4°F
7 1889 66.4°F
8 1902 66.4°F
9 1893 66.5°F
10 1892 66.6°F

Wettest Aug 11 – Sep 10 on Record

# Year Total
1 1955 16.88"
2 1924 11.43"
3 1872 10.27"
4 2021 9.25"
5 1919 8.01"
6 1879 7.91"
7 1905 7.81"
8 1888 6.87"
9 1994 6.63"
10 1873 6.45"

Driest Aug 11 – Sep 10 on Record

# Year Total
1 1995 0.04"
2 2007 0.09"
3 1883 0.47"
4 1981 0.49"
5 1978 0.52"
6 1960 0.82"
7 1982 0.86"
8 1906 0.87"
9 2013 0.90"
10 2024 1.04"
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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