A Mid-Atlantic Cold Day in July

July 22 Update: For the record, the National Weather Service report:

A RECORD LOW MAXIMUM TEMPERATURE OF 71 DEGREES WAS SET AT WASHINGTON   
NATIONAL DC YESTERDAY...JULY 21ST. THIS BREAKS THE OLD RECORD OF 74   
DEGREES THAT WAS SET IN 1984...1939 AND 1886.  

The Dulles and Baltimore/BWI records were 69°.

1 AM Update: And the 1 am temperature is again 70°, so the new record low maximum is pretty well set.

Some remedial math for Tom Nelson fans:
Total area of District of Columbia: 68 sq. mi.
Total area of Maryland: 12407 sq. mi.
Total area of U.S.: 3,794,100 sq. mi.
Total number of days in July: 31

Midnight Update: The temperature has held at 70° for 5 out of the last 6 hours, so the final high is likely to remain at 71°, setting a new record for July 21.

Attention Tom Nelson fans: Here is the context he's left out:
Washington on Track for 3rd Top-3 Hottest July in As Many Years

Original Post:
Some sun could still break through and nudge the temperature up a few degrees, but the high temperatures so far today in the Washington/Baltimore area are likely to break records for the coldest maximum on July 21:

Location            High Departure Previous record
Washington National  71   -18      74 /1984
Washington Dulles    68   -20      75 /1984 
Baltimore BWI        69   -18      73 /1984 

Although the 18 to 20 degree departures from average are spectacular, the same low clouds, drizzle, and light rain which depressed the daily highs have also kept the daily lows elevated, so the overall averages are in the -10° to -11° range relative to climatology.

The daily average of 69° at Washington National, if it holds, will be the 3rd coldest July 21 since 1929, when the average was 68°. The average on this date in 1939 was 68.5°. The low in 1929 was accomplished the old-fashioned way, with a daily low of 58°. The record low for July 21 was 56° in 1909.