A frightful or delightful Halloween?

 

Halloween in Potomac, Maryland

This October will finish as both a warmer and drier than average month in the nation’s capital for the seventh time in the last decade. Halloween will also be a dry day with near average high temperatures. That’s in contrast to 2024 when DC’s experienced its warmest Halloween since 1950, with a high temperature of 83°. DC’s average high/low temperatures on October 31 are 64°/46°.

The nation’s capital will finish the month with six days of 80-degree October warmth. That’s above the average of between three and four such days. A record high of 90° occurred in the nation’s capital on October 14. That was also the first 90-degree October heat since 2019. It also set a new record high for latest in the calendar year that 90-degree heat occurred. Eleven of the first 16 days of October were warmer than average in Washington, D.C.

Despite the warm start to October, eight days since October 17 were cooler than average. Although lows downtown fell to 42° twice this month, Dulles Airport has been in the 30s six times in the last two weeks. Meanwhile, it hasn’t been at or below freezing at National Airport during the month of October since 1992.

Measurable rainfall occurred in the nation’s capital on eight of the first 17 days of the month, but none has occurred since October 17. Since today will also be dry, the nation’s capital finish with below average October rainfall for the eighth time in the last decade. The 2.08” of rain this month is well below DC’s October average of 3.66”.

The dry conditions on Halloween should please trick-or-treaters. Temperatures for trick-or-treat this evening will be in the 50s. The last time Washingtonians had measurable rainfall on Halloween was in 2022.

Warmest October’s in Washington, D.C. (Source: NOAA)

1. 67.1° - 2007
2. 66.3° - 2021
3. 65.2° - 1984
4. 64.9° - 2017
5. 64.7° - 1971
6. 64.5° - 1947
7. 64.4° - 1941
8. 64.1° - 2019
9. 63.4° - 1949
10. 63.3° - 1973
11. 63.2° - 1975, 1919
12. 63.1° - 2023, 2016
13. 63.0° - 2024, 1879
14. 62.9° - 2014, 1881
15. 62.8° - 1990

Warmest October’s at Dulles Airport in Sterling, Virginia (NOAA)

1. 63.6° - 2021, 2007
2. 61.8° - 1984
3. 61.4° - 1971
4. 61.1° - 2017
5. 60.5° - 2019
6. 60.2° - 2023
7. 60.0° - 2026
8. 59.4° - 2016
9. 59.3° - 1963
10. 58.8° - 2005

Remembering destructive Sandy

 

Sandy in late-October 2012 (Source: NOAA)

Today is the 14^th anniversary of “Superstorm” Sandy’s landfall in New Jersey. The infamous storm had been a Category 3 hurricane with sustained winds of 115 mph and a minimum central air pressure of 940 millibars. It was the strongest hurricane of the active 2012 Atlantic hurricane season. 

However, shortly before its landfall in New Jersey, Sandy moved over cooler water and into an increasingly unfavorable environment for a tropical storm or hurricane. Consequently, the structure of the storm changed and the National Hurricane Center declared Sandy to be a “non-tropical” or “post-tropical” storm. That caused a lot of confusion for residents of the Mid-Atlantic and Northeastern United States who thought Sandy was no longer a threat since the hurricane watches and warnings were discontinued after it was declared “post-tropical.” 

At the time, Sandy was instead dubbed a “Superstorm” and made landfall as the equivalent of a Category 1 hurricane with sustained winds of 80 mph and a minimum central pressure of 946 millibars. As Sandy transitioned to a non-tropical storm, its wind field and rain shield each increased in diameter. That allowed for a larger geographic area to be impacted. 

Baltimore, MD; Philadelphia, PA; Trenton, NJ; and Atlantic City, NJ all set records for the lowest air pressure reading, according to NOAA. The lower the air pressure is, the stronger the storm is and the higher the winds tend to be.

Record flooding occurred in New Jersey, New York City and on Long Island, N.Y. with epic storm surges. Tens of thousands were left without electricity or heat for weeks. Record rainfall totals also occurred in the DMV (DC, Maryland and Virginia) with the following two-day rainfall totals:

October 29:  DCA (National Airport): 3.85” / Dulles Airport (IAD): 4.26” / BWI: 5.51”

October 30:  DCA: 0.84” / IAD: 1.00” / BWI: 0.92”

Eye-popping snowfall totals also occurred as Sandy pushed further inland and reached some of the higher elevation of the Appalachian Mountains. In West Virginia, for example, Richwood saw 36” of snow, Snowshoe got 32” and Davis had 28”. In all, Sandy did an estimated $88.5 billion in damages (2024 dollars) and is the fifth most destructive “hurricane” in U.S. history. Sandy also caused 147 direct fatalities in the United States largely due to storm surge, flooding and downed trees, according to NOAA.

DC’s volatile October weather

 

An October day at the farm

October is a transitional weather month as average daily temperatures and the amount of daylight each decrease throughout the month. That’s not to say there aren’t very warm October days in the nation’s capital, much like early winter’s chill can also occur.

Given the decreasing daily amount of sunlight and lowering sun angle as October wears on, it gets harder for very warm weather to occur. That said, there’s been no shortage of unusually warm October weather in recent years. For example, DC’s hottest October temperature on record of 98° occurred on October 2, 2019. To add to that, Halloween’s high temperature of 83° in 2024 was the warmest October 31 in the nation’s capital since 1950.

DC has averaged between three and four October days with highs in the 80s over the last 30 years. This month has already featured five days with highs in the 80s. Although 90-degree October heat is less common with only one such occurrence roughly once every four years, DC residents experienced 90-degree heat on October 14 (90°). That also set a new record for latest in the calendar year that 90-degree heat has occurred.

October lows in the 30s also occur on occasion in the nation’s capital. Such chilly temperatures, however, have been less common in recent decades. Washington, D.C. has averaged only between one and two October days with lows in the 30s over the last 30 years, with the most recent on October 19, 2022 (38°), according to NOAA data. 

There hasn’t been an October temperature at or below freezing in the nation’s capital since 1992. That can be attributed in part to a warming climate, as revealed in NOAA’s updated climate averages for the period of 1991-2020. The relatively warm decade of the 2010s replaced the cooler 1980s for this update. Also, there’s a more pronounced urban heat island effect now than in past decades due to increased urbanization and automobile traffic. Eight of DC’s 15 warmest October’s have occurred over just the last two decades.

DC’s warmest October’s (Source: NOAA)

1. 67.1° - 2007
2. 66.3° - 2021
3. 65.2° - 1984
4. 64.9° - 2017
5. 64.7° - 1971
6. 64.5° - 1947
7. 64.4° - 1941
8. 64.1° - 2019
9. 63.4° - 1949
10. 63.3° - 1973
11. 63.2° - 1975, 1919
12. 63.1° - 2023, 2016
13. 63.0° - 2024, 1879
14. 62.9° - 2014, 1881
15. 62.8° - 1990