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Posted at 11:03 AM ET, 05/01/2012

April 2012: 21st warmest on record (tied) - barely warmer than March; 30th driest

After the warmest and top ten driest March on record , April brought back a sense of weather normalcy. While relatively warm (1.5F warmer than normal) and dry (1.1” drier than normal), the month didn’t produce many extremes. But compared to March, April offered more weather variety: with more cooler-than-normal days and at least a few rainy/cloudy days.

The table to the right shows the years ranked between 20th and 24th warmest on record, with 2012’s average of 58.3 degrees in the middle. Four years have been warmer than April 2012 in the 2000s: 2011 (58.8F), 2010 (60.9F), 2006 (59.5F), 2002 (60.0F)

For precipitation, April 2012 was drier than normal, but the estimated 1.92” was still much more than the driest 0.03” from 1985. The wettest April on record continues to be 1889 with 9.1”.

Washington Reagan National (DCA) did not report any temperature or precipitation records this month. But Baltimore tied the 2002 record of 90F on April 16. Washington Dulles had a record high low temperature of 61F on April 16 and then a record low high temperature of just 47F just a week later on April 23.

Reagan National spent most of its days with highs in the 60s and lows in the 40s (almost two-thirds of the month had lows in the 40s).
Distribution of high and low April temperatures at Reagan National Airport

Comparison with March

After a record-warm March, many parts of April felt colder. While the average temperature in April is estimated to have been 1.4F warmer than March, we actually saw a higher frequency of the warmest temperature days in March compared to. April. For example, the DCA reported 14 days at or above 70F in March, but only 12 such days in April! Also, we were in the 80s four times in March, but only three times in April. It is as if our calendar reversed on us!
Comparison of number of 70+ and 80+ days in April and March at Reagan National Airport

Unlike March (and much of the past winter for that matter!), the warm ridging pattern in April was centered more over the Plains and less over the East Coast. This allowed for more East Coast pattern variability and some interior areas of the East to see the monthly average close to normal or even slightly cooler as a result. You can see the main warm ridge (northward buckle in the jet stream) on the map below for April 1-28.
Prevailing jet stream during April (NOAA)

And May?

Despite the very warm first handful of days in May, the pattern trends are suggesting a cooler situation by next week and maybe even deep into the month. Developing blocking patterns in high latitudes of North America means we would see more chances for cooler Canadian air transport in the weeks ahead. I’m not ready to suggest that May could be our first cooler-than-normal month since October, but this is probably the best chance since that time.

The National Weather Service offers a very large shoulder shrug with EC for both temperature and precipitation throughout our area. EC means Equal Chances of below, normal, or above normal temperatures (33.3 chance each).

Additional reading

The National Weather Service publishes nice monthly assessments usually within a week of the close of each month (should be available shortly):

You can click on your closest airport location here:

Reagan National (DCA)

Dulles Airport (IAD)

Baltimore-Washington (BWI)

Historical Washington, DC data provided by Speedwell Weather and NOAA. See also: Ian’s excellent rundown on April climatology

By  |  11:03 AM ET, 05/01/2012

Categories:  Latest, Local Climate

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