The Washington PostDemocracy Dies in Darkness

Baltimore–that is BWI Airport–logs 4th record low this July

Docks on the Potomac. (carolinejangelo via <a href="" target="_blank">Flickr</a> )

It’s incredible, on the streets of Washington-Baltimore region, we see people in jackets and holding their arms together – on July 29!  Lows this morning dipped into the 50s in many parts of the region and are struggling into the mid-70s this afternoon.

At BWI Airport this morning, this mercury dipped to 59  degrees, matching the record low from 1978.  This is the 4th time this month BWI has reached a record low.  Here are the other three cases:

  • July 5: 55°F (tie with 1979)
  • July 18: 57°F (besting 58 from 1976)
  • July 25: 57°F (besting 59 from 2008)

WBAL meteorologist Tony Pann notes Baltimore has set 8 record lows in 2014, overall (January-July).

Before we get carried away by this flurry of records and lest anyone fear Baltimore’s headed into an ice age, it’s important to appreciate that it’s somewhat easier for Baltimore to set record lows now because it’s observing station – which had been downtown at the U.S. Custom House from the late 1800s through 1950 – was moved to BWI Airport. BWI Airport – located in northern Anne Arundel County – is much less urbanized location than downtown Baltimore, so overnight temperatures in particular tend to be cooler. There is less of an urban heat island effect, in which concrete and asphalt surfaces retain heat near the ground.

This is – in a sense – the opposite situation from Reagan National Airport where it has become more difficult to set record lows since it resides in a location that has become more urbanized over time. Like Baltimore, a weather station for D.C. was also located in the city (at 24th and M St.) prior to its move to Reagan National Airport (in 1945) but differences in overnight low temperatures between Reagan and 24th and M (both urban locations) are no doubt smaller than differences between BWI and Custom House (suburban and urban).

Related links:

Reagan National Airport’s misleading low temperatures

Should Reagan National Airport remain Washington, D.C.’s official weather station?

Warm temperature records dramatically outpacing cold records in Washington, D.C.