DC’s Warm Start to October

Seven of the first nine months of 2018 were warmer than average in the Nation’s Capital.  The combination of this trend with NOAA’s forecast for above average October temperatures means this week’s warmer than average weather shouldn’t come as a surprise to anyone in the DC Metro Area.

Despite only one 90° day this month, October 2018 has gotten off to an exceptionally warm start.  Not since October 2013 have Washingtonians experienced at least four days with high temperatures of at least 81° to start the month.  Five of the last six Octobers have been warmer than average in the Nation’s Capital.  

Given the rainy second half of September with rain on eight of the final 10 days of the month, this warm and dry start to October has been welcomed by many DC area residents.  In fact, yesterday’s high temperature of 90° at National Airport was DC’s first 90° day since September 7 (91°).  Having 90° heat in October is rare in the Nation’s Capital, occurring roughly once every four to five years since 1993.  DC’s warmest October temperature on record is 96° (October 5, 1941) while the latest date in the year it has been 90° is October 11.  

By October, the length of daylight and sun angle are both significantly lower than during the summer.  Only one heat wave (3 or more consecutive 90° days) has occurred in the Nation’s Capital during the month of October in the last 25 years (October 7 – 9, 2007).  Average high temperatures in the Nation’s Capital fall significantly during the month of October from 74° to 64° by Halloween.

Area residents may recall that October can feature some very rainy and chilly conditions.  Record low high temperatures in the 40s occurred on October 16-17, 2009, while an early season Nor’Easter brought 1.2” of rain to DC on October 17, 2009.  More recently, a record low-high temperature of 42° occurred on October 29, 2011 with a trace of snow (not enough to measure).  A record “low-high” temperature means the 42° was much colder than the average high for the date of 64°.

Despite NOAA’s forecast for above average temperatures through mid-October across much of the eastern United States, the DC Area could see some cooler than average temperatures.  However, the overall weather pattern favors warmer and drier than average conditions for the DC Metro Area over the next few weeks.  By the end of the month, it is probable that October will become DC’s eighth warmer than average month of 2018.