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October 2021 Summary – Sixth Warmest on Record

November 5, 2021

Blue Hill Observatory October 2021 Summary: October was very warm and much wetter than average. The 24-hour adjusted mean temperature for the…

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Visible satellite imagery of Nor’easter on 27 October 2021. Imagery courtesy of weather.cod.edu.

Blue Hill Observatory October 2021 Summary:

October was very warm and much wetter than average. The 24-hour adjusted mean temperature for the month of 56.3 deg F was 5.0 degrees warmer than the 1891-2020 130-year average for October, and it was 4.1 degrees warmer than the 1991-2020 30-year average. The month was the sixth warmest October on record and the warmest since 2017. The average maximum temperature of 64.1 deg F was 3.5 degrees warmer than the 130-year mean. The average minimum temperature of 49.4 deg F was 5.8 degrees warmer than the 130-year mean, and the average minimum was the third warmest on record. Only nine days during the month were cooler than average. The highest temperature observed all month was 75F on the 13th, and the lowest temperature during October was 37F on the 24th and 29th. The low temperature of 37F on the 24th tied as the latest date on record of the first fall temperature below 40F. The mean water vapor pressure during the month was 12.9 mb, which reflected the high level of moisture in the air during October and was the second highest on record for the month. October total precipitation was 7.87 inches, which was nearly four inches more than the 130-year average and two and a half inches more than the 1991-2020 30-year mean. October was the 11th wettest on record. Most of this rainfall occurred during three rainfall events, including 2.08 inches on the 3rd-5th, 2.38 inches during a strong coastal storm on the 26th-27th that also brought damaging winds to eastern MA, and 1.69 inches on the 30th-31st. The heaviest rain occurred in the early evening of the 30th with 0.52 inches in the hour from 5-6 PM EST. The greatest rainfall in 24 hours for October was 2.23 inches on the 26th. There were no thunderstorm days during October. The mean wind speed for the month was 11.4 mph, which was the third lowest on record, and the prevailing wind direction was from the west-northwest. The highest wind gust was 66 mph from the NNE during the strong coastal storm on the morning of the 27th. October sunshine was below average with 174.9 hours of bright sunshine, which was 53 percent of the possible sunshine and two percent less than the 130-year mean.

BHO Warmest October 24-Hour Corrected Mean Temperature, deg F (1885-2021):

1) 59.2 in 2017
2) 58.4 in 1947
3) 56.9 in 2007
4) 56.6 in 1971
5) 56.5 in 1963
6) 56.3 in 2021
7) 55.7 in 1946
8) 55.5 in 1995

BHO Warmest October Average Minimum Temperature, deg F (1885-2021):

1) 51.7 in 2017
2) 49.5 in 2007
3) 49.4 in 2021
4) 49.2 in 1971
5) 49.1 in 1947

BHO Latest First Fall Temperature Below 40F, deg F (1885-2021):

1) 36 on 24 October 2013
   37 on 24 October 2021
3) 34 on 22 October 1955
4) 39 on 21 October 2005
5) 38 on 20 October 1960
6) 39 on 19 October 2014

BHO Highest October Average Water Vapor Pressure, mb (1932-2021):

1) 13.2 in 2017
2) 12.9 in 2021
3) 12.7 in 2007
4) 12.4 in 1971
5) 11.9 in 2012
11.9 in 1990

BHO Lowest October Mean Wind Speed, mph (1885-2021):

1) 11.2 in 2013
2) 11.3 in 2020
3) 11.4 in 2021
4) 11.8 in 1997
11.8 in 2016

Mike Iacono
Chief Scientist
Blue Hill Observatory

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Blue Hill Observatory & Science Center · Legal

Data Use & Privacy Policy

Please read the full Policy before accessing Observatory data · Effective January 1, 2025

Notice: By accessing, downloading, or using any Blue Hill Observatory data or services, you unconditionally accept and agree to be bound by this Policy in its entirety. If you do not agree, you may not access or use Observatory data.
Effective January 1, 2025 · Milton, Massachusetts · bluehill.org
Part I — Data Use Policy
§ 01

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§ 02

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§ 03

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§ 04

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§ 05

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§ 06

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§ 07

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§ 08

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§ 09–10

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§ 13

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§ 17–20

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Effective January 1, 2025 · Blue Hill Observatory & Science Center · Milton, Massachusetts
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