Will Halloween Bring Tricks or Treats?

October sunset in Poolesville, MD  (Courtesy: Ashley Adams)

Late October typically brings the Nation’s Capital a high degree of variability in the weather from one year to the next.  That contributes to making it especially challenging to accurately forecast the weather on Halloween more than a few days in advance.  A good example of this changeable weather occurred on this date in 1996 when a record high temperature of 82 degrees was set at National Airport.

By contrast, Washingtonians saw a truly rare event on October 29, 2011 when the first snow of the season fell.  Temperatures also remained more than 20 degrees below average as the daily high temperatures at both National and Dulles Airports hovered close to 40 degrees.  That left many longing for the record warmth experienced in 1996.

Such radically different weather conditions can be largely attributed to the position of the jet stream.  In 1996, the jet stream was well to our north, which allowed an area of high pressure (situated off the east coast of the United States) to usher in the record warmth.  However, there was a significant dip in the jet stream 15 years later that facilitated the significantly colder than average weather in 2011.  According to the National Weather Service, today’s average high is 64 degrees at both National and Dulles Airports.

Temperatures have been cooler than average with highs remaining in the 50s on three of the last four Halloweens.  High temperatures are poised to be around 60 degrees tomorrow in Washington, D.C.  The coldest Halloween during the last 20 years in the Nation's Capital came in 2002, when it was only 47 degrees; while the warmest Halloween to occur in recent memory was in 2004 when it was 79 degrees.  Many trick-or-treaters may also remember that measurable rain hasn’t occurred in the DC Metro Region on Halloween since 2009.  Looking ahead to the first week of November next week, temperatures will feel more like September, as it will soar well into the 70s across the Mid-Atlantic Region. 

Tomorrow night is also when Daylight Saving Time ends, so we need to set our clocks back one hour.  The good news about changing the clocks back is that it will make this weekend 49 hours long.  In the interest of safety, it’s a good idea to also change the batteries in our smoke and carbon monoxide detectors this weekend.