Given our recent battle with temperatures in the mid-90s, we aren’t gently easing into summer. But at least we can enjoy some relief through the weekend.
The past week’s weather may well be a microcosm of what lies ahead this summer — periods of high heat and humidity but some enjoyable reprieves, as well.
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Overall, we project close-to-normal summer temperatures and a reasonably strong chance to avoid historic heat.
If this idea works out, it would be a welcome change. Over the last dozen years or so, our summers have been overwhelmingly hot and humid. Eight of our 10 hottest summers on record have occurred since 2010. Last year tied as our eighth hottest summer on record, with 48 days hitting at least 90 degrees (the normal is 40).
But we think this summer has a 50-50 shot to be the coolest summer since 2014. Granted, what we consider cool is relative, as temperatures are on the rise because of climate change.
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Our outlook requires interpretation within the context of a very hot last 30 years of weather data. Our latest climate “normals,” based on the period between 1991 and 2020, are 1.2 degrees higher than the normals between 1981 to 2010.
Washington’s new climate ‘normals’ are hotter and wetter
While each of the past 10 summers was warmer than 1981-2010 normals (77.7 degrees), three of them would be cooler than 1991-2020 normals (78.9 degrees). Our forecast for this summer’s average temperature is slightly hotter than the old normals and a little lower than the new normals.
In other words, we’re not forecasting this summer to be either exceptionally hot or memorably refreshing. Rather, we expect this summer to be hot and humid, like almost all D.C. summers.
Compared with outlooks issued by other groups, ours is an outlier. The National Weather Service, AccuWeather and The Weather Company all lean toward hotter-than-normal conditions. However, we agree with the Weather Service and the Weather Company that June will be slightly warmer than normal.
Computer models also generally project a somewhat warmer-than-normal June and are mixed about what to expect in July and August.
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The weather pattern, alternating between uncomfortably muggy and tolerable, will probably support a fair share of storminess. We lean toward above average summer rainfall — continuing the pattern we saw in May — our 14th wettest on record.
Our outlook for this summer is similar to the one we issued for last summer. That forecast turned out to be a little too cool, as we predicted slightly below-normal temperatures, and they were slightly above normal.
When putting together a summer outlook, we’re less likely to see the signals for warmer- or cooler-than-normal weather (relative to average) that we sometimes see in advance of winter. As such, our outlook is of low confidence. This kind of seasonal forecasting is experimental, and errors are possible.
Summer outlook by the numbers
Summer average temperature: We project the average temperature to range from near normal to one degree below normal.
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Temperatures compared to normal month by month:
June: 1 degree above normal July: 1 to 2 degrees below normal August: 1 degree below normal
Number of 90-degree days for June, July and August: 28-35, compared with the normal of 34. Note that an additional six 90-degree days occur on average outside June to August. So far this year, we have three.
Longest streak of 90-degree days: Five to seven days
Number of 100-degree days: None
Precipitation: Somewhat-above-average rainfall
Methodology
We considered several factors, described below, in preparing this outlook. It should be noted that any one factor doesn’t necessarily correlate with a particular kind of summer (e.g., warm, cool, dry or wet).
We are currently experiencing the La Ni？a phase of the El Ni？o Southern Oscillation, and we expect it to persist through the summer even as it continues to weaken a bit from its winter peak.
The presence of either El Ni？o or La Ni？a in the tropical Pacific Ocean sometimes makes predicting summer conditions easier, as El Ni？os can favor cooler summers, while La Ni？as often favor hotter summers. However, we don’t expect this La Ni？a event to be a dominant factor in our weather, because it’s weakening.
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In addition to La Ni？a, we considered the current phase of the Pacific Decadal Oscillation (persistently negative) and predecessor weather patterns from the spring. These inputs informed the identification of analogues, or years with similar weather patterns, that we used in putting together our outlook.
In this case, the summers of 1950, 1956, 1971, and 2000 emerged as the best analogues. The weather during those summers was given some loose consideration in our projections for the one that is now beginning.
Looking back at May
May was a muddled month as we closed out springtime.
Temperatures were chilly at times, with the coolest lows in the low 40s, and then quite hot, like Tuesday’s maximum of 96, the highest during the month in more than a decade. Taking everything together, the month ended 0.6 degrees warmer than normal with an average temperature of 67.8 degrees. It was the 31st warmest May on record, tying 2007 and 2000.
The fluctuating temperatures were a reflection of a stormy pattern, with measurable rain on 14 of the 31 days. The monthly total was 6.36 inches (2.42 inches above normal), marking the second wettest May of the past decade and helping 2022 to run wetter than normal overall.
As temperatures rose during the final third of the month, Dulles Airport set several record high temperatures:
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May 21: A record warm low of 73 and record high of 92, tied with 1996 May 22: A record high of 91 May 31: A record high of 94, tied with 2011
Dulles also set a rainfall record on May 7, picking up 1.18 inches. Only one record was set in Washington: On May 21, the low of 73 was the warmest observed for the date. No records were set in Baltimore.
At the end of April, we correctly predicted near-normal temperatures during May, projecting a range between 65 and 69 degrees. Our rainfall forecast was less successful. We called for slightly above-normal amounts between 3.8 and 4.5 inches, which was about two inches too low. We’d grade our April outlook a B.
Year-to-date temperature and precipitation
Tracking temperature and precipitation year-to-date shows 2022 running slightly warmer and wetter than normal than last year, but not to extreme levels:
Past summer outlooks and evaluations
CWG’s 2021 summer outlook (We did not evaluate this outlook, but the results are summarized above.)
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CWG’s 2020 summer outlook (post-summer evaluation)
CWG’s 2019 summer outlook (post-summer evaluation)
CWG’s 2018 summer outlook (We did not evaluate this outlook, but we did well calling for the summer to average one degree above normal, and it ended up two degrees above normal. In addition, we projected 35 days at or above 90 between June and August, which was the exact number.)
CWG’s 2017 summer outlook (post-summer evaluation)
CWG’s 2016 summer outlook (post-summer evaluation)
CWG’s 2015 summer outlook (post-summer evaluation)
CWG’s 2014 summer outlook (post-summer evaluation)
CWG’s 2013 summer outlook (post-summer evaluation)
CWG’s 2012 summer outlook (post-summer evaluation)
CWG’s 2011 summer outlook (post-summer evaluation)
CWG’s 2010 summer outlook (post-summer evaluation)
CWG’s 2009 summer outlook (post-summer evaluation)