Washington, Oct. 28. (John Sonderman via Flickr)

October supplied plenty of ammunition for all the people complaining about a delayed start to autumn, as well as those concerned about the warming climate. The month ranked as the third warmest October on record in Washington, 5.4 degrees warmer than normal.

All but two months in 2017, May and August, have been warmer than normal, and February and April ranked as warmest on record. The year ranks as the second warmest on record so far, narrowly behind 2012.


Washington’s balmy October weather best matched typical conditions in Atlanta, according to the Southeast Regional Climate Center.

The beginning of the month felt much more like summer than fall. From Oct. 5 to 10, the temperature soared to at least 80 degrees on six straight days — tied for the fifth longest such stretch on record during the month.

Morning low temperatures resembled the mugginess of mid-July. From Oct. 8 to 10, lows only fell to 75, 74 and 72 degrees — all daily records. The low of 75 on Oct. 8 was the highest ever recorded in the month of October.

The humidity was also sky high. The dew point, a measure of humidity, remained at least 70 degrees for nearly three straight days Oct. 8 to 10 — the longest stretch on record for the month by far, nearly doubling the next longest streak (1.5 days in 1959).

Even during the second half of the month, temperatures were considerably warmer than normal — with the majority of days reaching at least 70 degrees.


The coolest weather, compared to normal, came at the very end of the month when high temperatures were close to 60 and lows dipped into the 40s. That last-minute cooling prevented October from becoming the warmest on record in Washington.

The monthly average temperature fell a couple degrees below 2007’s record, and also ended up a smidgen cooler than 1984, to rank third warmest since records began in 1871:

Not only was it unusually warm, but also quite dry. The monthly precipitation total of 2.02 inches was 1.38 inches below normal. It ranked as the sixth driest of the 2000s. Only the coastal storm to close out the month, which dispensed 1.06 inches Oct. 29-30, saved it from being even drier.

The combination of the dry September, when rainfall was 2.29 inches below normal, and October have marginally pushed the year’s precipitation total into below normal territory:


Records

The big story was a three-day string of record-warm low temperatures during which two of our three official observing stations (Washington and Dulles) posted their warmest October low temperatures in recorded history.

Washington

  • Oct. 8: Record warm minimum of 75 degrees tops 68 from 2007.  This was also the warmest low temperature for the month of October.
  • Oct. 9: Record warm minimum of 74 degrees tops 72 from 1959.
  • Oct. 10: Record warm minimum of 72 degrees tops 69 from 1990.

Baltimore

  • Oct. 9: Record warm minimum of 74 degrees tops 68 from 1922.
  • Oct. 10: Record warm minimum of 72 degrees tops 71 from 1959.

Dulles

  • Oct. 8: Record warm minimum of 73 degrees outperforms 66 from 1976.  This was also the warmest low temperature for the month of October.
  • Oct. 9: Record warm minimum of 69 degrees tops 66 from 1990.
  • Oct. 10: Record high temperature of 87 tops 85 from 1985.

October weather pattern

For the most part, a warm dome of high pressure at high altitudes resided over the eastern United States in October. This promoted the nation’s warmest weather compared to normal in this region:



October forecast review

Here was what we wrote a month ago:

“Overall, we favor October to end up somewhat warmer than normal (by 0.5 to 2 degrees), but the pattern has a chance to change to a cooler one by the middle of month. For this reason, we don’t think it will be as warm as last year, when it ended up four degrees above average.”

In reality it was 5.4 degrees above normal. However, we issued a second update on Oct. 6 in which we said the month could rank among the warmest on record, which was correct.

For precipitation, we predicted “the month will be slightly drier than normal (1.5 to 3 inches versus normal of 3.4 inches), but not as dry as last year when just 0.9 inches of rain fell.” That prediction was on the money considering the total rainfall of 2.02 inches.

Forecast grade: B+ (both forecasts were directionally correct — warmer and drier than normal)

What do you think? Tell us in the comments.