June is the start of meteorological summer, and in Washington, D.C. that means the weather starts to settle into a mostly predictable pattern that features mainly a persistent and growing heat and humidity regime, intermixed with the occasional – sometimes quite energetic – volley of showers and thunderstorms.
By June, the storm track typically lifts into a position where the most continual rainfall activity passes to our north and west. But, depending on the location of the season’s heat ridging, some systems break through and temporarily send us back into springtime bliss, or t’storm complexes ride around the building summertime high pressure, occasionally targeting the area.
Keep reading for more in this third installment of a year-long series of posts detailing specific statistics on climate norms, extremes, and averages for the each month in Washington, D.C…PRECIPITATION
The average rainfall in June is 3.77” (previously 3.13” from 1971-2000)*. An extremely wet June in 2006 helped boost this raw average, though numerous seasons in the 30-yr period featured much above average rain at the time it fell.
The maximum rainfall on record for June was during that very wet one in 2006, when 14.02” of rain fell. Two other Junes have featured rainfall over 10”. D.C.’s driest June came in 1940 when 0.86” of rain fell. Much of June’s rain comes in thunderstorms, and June ranks a very close second to July in thunderstorm days.
The most rain that has fallen on one day in June is 6.11” on the 21st in 1972. By June, we really begin to feel the influence of increased atmospheric moisture, and while it ranks lower than some other months for monthly rain (largely due to variability in storm track), rainfall can be very intense when it occurs. 28 June days have seen totals in excess of 2”.
As noted above, June saw a large step up in raw averages for monthly precipitation. In fact, it was the greatest change of any month from 1971-2000 to 1981-2010. A significant factor was June 2006, which featured a front stalling over the region and interacting with copious moisture to produce over 10” of flooding rain in two days in D.C.
If tossing the outlier record month (plus the lowest of the 30-yr, 0.95 in 1988), the average for the period becomes 3.51”. From 2000-2009, every June except 2 were above average, but the low ones were quite below average, as was 2010. Summer can be feast or famine in D.C. with precipitation, but it’s usually just a feast with warmth…TEMPERATURES
June’s monthly average temperature is 74.5 degrees (per NWS 1971-2000 norms**), a gain of about 9 degrees from May. It has been as warm as 80.6 in the record-breaking June of 2010 and as cool as 65.9 in 1907.
We start the month with an average high above 80-degrees and never look back. Highs are largely in the 80s (55% of the time), but it’s also more likely to see highs in the 90s than the 70s (23% v. 19%). The lowest high temperature in June was 52 on the 6th in 1894 and the highest was 102 on the 9th in 1874.
Low temperatures continue their climb in June, and those window-open and no A/C nights rapidly dwindle or disappear. A majority (52%) of the lows fall in the 60s, with 34% in the 70s and 14% in the 50s. The lowest low temperature in June was 43 in 1897 (46 at DCA in 1945), and the highest low was 82 in 1991.
June brings about 20% of D.C.’s 90-degree or greater days during the year. The average, around 7, is half that of July, and a few less than August. 100-degree heat, sort of uncommon on the whole, is even more so in June, visiting about once every 10 years. The only time there was back-to-back Junes with 100-degree days was during the super-hot Dust Bowl era in 1933 & ‘34.DATA
30-year (1981-2010) Averages / Overall (All history) Averages...
Highs 85 or above: 16.0 / 14.2
Highs 90 or above: 7.1 / 6.5
Highs 95 or above: 1.8 / 1.4
Highs below 80: 6.7 / 8.6
Lows below 60: 4.1 / 6.9
Lows 70 or above: 10.1 / 6.6
Days with a trace of rain: 14.7 / 14.6
Days with .1” of rain or more: 6.1 / 6.4
Days with .5” of rain or more: 2.5 / 2.5
Days with 1” of rain or more: 1.0 / 1.0
Days with thunder:7.0 / NA
Days with hail: 0.2 / NA
-This count is done through records on Weather Underground, and does not include the entire historical period.
All-Time Records (High / Low)...
Highs 85 or above: 25 (1994) / 1 (1903)
Highs 90 or above: 18 (1943, 2010) / 0 (6 years)
Highs 95 or above: 7 (1995, 2010) / 0 (57 years)
Highs below 80: 23 (1903) / 2 (7 years)
Lows below 60: 20 (1907) / 0 (6 years)
Lows 70 or above: 22 (2010) / 0 (8 years)
Days with a trace of rain: 23 (1928) / 7 (3 years)
Days with .1” of rain or more: 13 (1883) / 1 (1940)
Days with .5” of rain or more: 7 (1989) / 0 (6 years)
Days with 1” of rain or more: 4 (3 years) / 0 (53 years)
Days with thunder:14 (2008) / 3 (1999)
-Same as above. (30-year high / low listed)
Daily climate records for Washington, D.C., 1871-present
- See selected and additional statistics compiled for this post (Excel)
*All averages, unless otherwise noted, refer to the 30-year period of 1981-2010.
**All instances of monthly temperature average, daily temperature average or daily precipitation average refer to the 1971-2000 climate normals as presented by the National Weather Service. NWS smooths some averages without daily data in a method described here. Monthly rainfall is a simple average and new 1981-2010 data is used here. NWS data on temperature averages should update shortly and will be reflected in these posts.ABOUT THIS SERIES
While numerous local climatology statistics including daily, monthly, and seasonal normals and records are available from National Weather Service Baltimore/Washington, there are myriad other pieces of information which help frame the story. Rather than attempt to recreate what is already available, this series of posts will act as a companion to most information presented there.
This is the third installment of a series of living documents. Through early 2012, each month will be broken down in a similar or evolving way. As input is taken from the community, some items may be added to or changed in older postings. These postings will be updated as necessary to reflect changes when needed. Other articles may also become part of this series.
Feel free to share thoughts or additional data you may be interested in seeing.
Learn more about each month:
Article last updated: June 9, 2011.