May gets underway !

 

A spring day at Lake Needwood, Derwood, Maryland

May completes DC's transition from winter to spring as the final month of "meteorological" spring.  It often feels like summer by the end of the month.

Average daily temperatures in May warm appreciably in the nation’s capital. Daily average temperatures range from a high/low of 73°/54° on May 1 to 80°/63° by the end of the month. DC’s hottest May temperature on record of 99° occurred on May 31, 1991. Meanwhile, DC’s coldest May temperature of 33° occurred long ago on May 11, 1906. 

DC’s May weather can be quite streaky. For example, four of DC’s 10 warmest May’s have occurred since 2012. By comparison, three of the last four May’s have been cooler than average, following DC’s very warm May’s in 2018 and 2019.  That's similar to last month that finished as DC's ninth warmest April on record and fifth April of the Top 10 to occur since 2010.

May is DC’s third wettest month of the year according to NOAA, with an average monthly rainfall total of 3.94”. Rain can accumulate quickly in the nation’s capital this time of year as May 2008 illustrated. That was DC’s third wettest May with 10.66” of rain and an incredible total of five days each with an inch or more of rain. On the other hand, three of the last four May's have been drier than average in Washington, D.C.

May is frequently an active severe weather month in the DC Metro Area.  Looking at DC’s May climate records, one can see that on several dates a trace of snowfall (enough to accumulate, but not enough to measure) has occurred.  Except it wasn’t actually snow, but hail.  For example, on May 2, 2016, a severe weather outbreak produced a lot of hail in the DC Metro Area.  Small accumulations of hail were reported in spots such as at National Airport where a “trace” of frozen precipitation was observed.

Although summer doesn’t officially arrive until June, May often features summer-like heat. The nation’s capital has averaged between one and two May days with highs in the 90s over the last 30 years, according to data from NOAA. DC residents can also expect to see a high of at least 95° roughly once every four to five years, with the last such occurrence being a high of 96° on May 31, 2022. 

NOAA’s Climate Prediction Center expects May 2024 to feature above average temperatures and rainfall in the nation’s capital.

DC's summer preview

 

A fine spring day in suburban Washington, D.C.

This month is finishing on a very warm note in the nation's capital. Today could become the first 90° April day in seven years since a record-tying high of 91° on this date in 2017. DC averages only one 90° April day every three to four years, based on NOAA data over the last 30 years.

April 2024 will finish as a warmer than average month in the nation's capital. Depending on how warm it gets today and tomorrow, this month could rank among DC's Top 10 warmest April's on record. That's notable since four of DC's 10 warmest April's have occurred in the last 14 years. 

What makes this month different is how streaky temperatures and rainfall have been. April got off to an unusually chilly start with below average temperatures on six of the first seven days of the month. That was followed by 11 consecutive warmer than average days, including April 15 that featured a high/low of 83°/63°. Seven of the following nine days, through April 27, were cooler than average in the nation's capital.

That's brought us to this June-like weather pattern to finish the month with several days in the 80s or higher. Unlike June, however, this week's temperatures will lack the muggy conditions that often accompany DC's summertime heat.

While it could reach 90° in the nation's capital this afternoon, it isn't a sure thing given National Airport's proximity to the Potomac River. If the wind direction is blowing from the south off the chilly water, then temperatures at the airport, DC's official weather reporting site, remain a few degrees cooler than downtown areas. While a south wind pumps more humid air into the nation's capital during the spring and summer, DC's hottest days occur when a more westerly wind occurs.

April 2024 will also finish as a drier than average month in the nation's capital. That's despite 1.68" of rain, more than half of DC's April rainfall average of 3.21", during the first week of the month.  Only 0.38" of rain has fallen since then, for a monthly rainfall total of 2.06". Despite the below average rainfall this month, no drought conditions exist in the DMV given how wet 2024 has been so far. The nation's capital has a yearly rainfall surplus of 2.29" since January 1.

Warmest April’s in Washington, DC (Source: NOAA)

1. 63.8° (2017)
2. 62.4° (2019)
3. 62.1° (2023, 1981)
5. 62.0° (1994)
6. 61.6° (1985)
7. 61.2° (1960)
8. 60.9° (2010)
9. 60.6° (1941)
10. 60.1° (1980, 1977)

DC's changeable April weather

 

Signs of spring abound around the DMV

Although it isn’t typically as cold in the nation’s capital in April as it is in March, it can still get chilly. Moreover, while April doesn’t often see weather as hot as in May, it can also be quite hot.

2021: Washingtonians experienced very streaky weather during April with above average temperatures on eight of the first 11 days of the month. However, there were only five warmer than average days the rest of the month. This led to DC's temperature for the month to finish at 58.2°, which is spot on average. Finishing with merely "average" temperatures for the month hides how streaky this month's weather was. DC's low temperature of 31° was the first at or below average April temperature since 2016.

2020: DC’s high temperature on April 13 was 81°, which was still significantly warmer than DC's average high temperature for the date of 66°. That was soon followed by four consecutive days with highs in the 50s through April 18, which is more characteristic of early March.

2017:  This was DC’s warmest April on record with an average temperature seven degrees above the average. Monthly average temperatures are comprised of daily high and low temperatures. All but seven days this April were warmer than average. April 29 was also the last time Washingtonians experienced 90° heat during April, with a record-tying high temperature of 91°. Four of DC’s 10 warmest April’s have occurred just since 2010. 

2007:  DC had three consecutive days of low temperatures at or below 32° from April 7 – April 9. The month finished 3.2° cooler than average, with an average temperature of 53.6°. This was also the last time Washingtonians experienced a record low temperature during the month of April, as the low fell to 29° on April 8.

2002:  April finished as DC’s 12^th warmest on record and featured a rare stretch of three consecutive 90-degree days from April 16 – 18. There was a record high of 95° on April 17 that also tied DC’s record high for the entire month of April.

Warmest April’s in Washington, DC (Source: NOAA)

1. 63.8° (2017)
2. 62.4° (2019)
3. 62.1° (2023, 1981)
5. 62.0° (1994)
6. 61.6° (1985)
7. 61.2° (1960)
8. 60.9° (2010)
9. 60.6° (1941)
10. 60.1° (1980, 1977)
12. 60.0° (2002)