Washingtonians should brace themselves for potentially the hottest summer since at least 2020, with long stretches of 90-degree weather and the chance to surpass the century mark for the first time since 2016. Factoring in the District’s trademark humidity, expect brutal, sauna-like conditions at times.
Even though D.C. summers are almost always hot and humid, this one could rank among the top summers in those categories. Our detailed outlook follows.
The summer will mark a continuation of a very warm start to 2024. Despite closing with some seasonably cool days, May will be the District’s sixth consecutive warmer-than-normal month. While we haven’t hit 90 degrees since a few weeks ago and the air is delightfully refreshing, summer always prevails as we progress through June.
Although we don’t think it will be a memorably hot summer like those in the brutal stretch from 2010 to 2012 — the three hottest on record — this summer should be noticeably warmer than last year’s, when the number of 90-degree days was actually below normal and the average temperature was 0.8 degrees cooler than the norm.
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Recent summers comparable to what we expect this year would be 2020 and 2016, which ranked fifth-hottest and third-hottest in records dating to 1872.
Assuming summer temperatures end up above normal as predicted, it’s worth noting that our “new normal” summer is hotter than it was a few decades ago. In other words, a summer that’s only somewhat warmer than normal in today’s climate would have been historically hot a few decades ago.
The area’s average high from July 6 to 27 is about 90 degrees, whereas it was previously in the upper 80s. Human-caused climate change has boosted average temperatures by over 1 degree in the past 30 years.
When putting together a summer outlook, we’re less likely to see the signals for extreme warmth or cold (relative to average) that we sometimes see in advance of winter. As such, this outlook is of low to medium confidence. This kind of seasonal forecasting is experimental, and errors are possible.
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This outlook covers the period known as “meteorological” summer — or June 1 through Aug. 31.
Summer outlook by the numbers
June through August average temperature: About 1 degree above the average from 1991 to 2020.
Temperatures compared to average by month:
- June: 1 to 2 degrees above average.
- July: 1 degree above average.
- August: 1 degree above average.
Number of 90-degree days for June, July and August: 40, compared with an average of 34. Note that an additional six days of 90-degree temps occur on average outside June to August.
Longest streak of 90-degree days: Eight to 10 days.
Number of 100-degree days: One to two.
Precipitation: Slightly below average.
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 experiencing a rapidly waning El Niño event, and there’s a strong possibility that a La Niña pattern develops by late in the summer. The presence of either El Niño or La Niña in the tropical Pacific Ocean sometimes makes predicting summer conditions easier, as El Niños can favor cooler summers, while La Niñas favor hotter summers. When conditions are neutral, as we expect this summer, the signal from the Niño regions isn’t as strong.
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In addition to El Niño and La Niña, we considered the persistently negative phase of the Pacific Decadal Oscillation 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 1998 and 2010 emerged as the best analogues. The weather during those summers was given some loose consideration in our projections for the one that is about to begin.
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