“Comparing forecasts for this summer versus last summer, it’s substantially cooler,” said Stephen Baxter, lead author of the National Weather Service’s summer outlook.

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But even if it’s not as hot as last summer, it’s still predicted to be plenty toasty — which is the emerging new normal.

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The National Weather Service outlook

If it weren’t for climate change, the National Weather Service might be predicting a cooler than normal summer in Washington. Baxter said its prediction for a somewhat warmer than normal summer was made largely on the basis that summer temperatures are trending hotter in recent decades. “It’s a fairly overwhelming signal,” he said.

The rising temperatures serve as “the backdrop” for the Weather Service’s warm summer forecast not just in Washington but for much of the East Coast, the South and the West.

But superimposed on the climate warming signal, developing atmosphere and ocean influences may take an edge off the summer heat. For one, high soil moisture levels over the Lower 48, thanks to prolific spring rains, should dampen the intensity of developing heat waves. Second, a weak El Niño may develop, which would also exert a slight cooling influence in the eastern United States.

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Subtracting these cooling influences from the long-term warming signal, Baxter predicts this summer’s heat in Washington to rank “close to the middle of the pack” relative to the past 15 summers. Bear in mind the last 15 years have been historically hot. So a middle of the pack summer in the present is markedly hotter than a normal summer from the past.

Private sector company outlooks

Summer outlooks are typically low confidence, and versions from different outlets frequently conflict with one another. But 2017’s summer outlook confidence is propped up by nearly harmonious agreement between the outlooks of private sector outlets and the Weather Service.

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AccuWeather

Paul Pastelok, AccuWeather’s chief long-range forecaster, calls for Washington’s summer temperature to average about one degree above normal — not far off the Weather Service’s estimate of 0.5 degrees above normal. He’s predicting 43 days at or above 90 degrees — which is right around the average of 40 over the past 15 years.

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“Warm Atlantic water temperatures should allow for some hot periods, but not persistent,” Pastelok said in an email. “Also, it does not look dry. It could be a rather active shower and thunderstorm summer holding back long periods of heat.”

Commodity Weather Group

The Commodity Weather Group, a private firm based in Bethesda, Md., also predicts the summer to be about one degree warmer than normal in Washington.

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But Matt Rogers, its president and a contributor to the Capital Weather Gang, sees the outside risk for a cooler than normal outcome. He pointed out Pacific Ocean temperatures are “almost identical” to 2014 when a weak El Niño was also trying to form (but ultimately did not), similar to this year. 2014 was the last time Washington had a cooler than normal summer, with just 24 days at or above 90 degrees.

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Joe Bastardi

Joe Bastardi, who leads long-range forecast efforts for WeatherBell Analytics, agrees with the idea of a slightly warmer-than-normal summer in Washington. In an email, he said he’s calling for 42 days at or above 90 degrees — just one different from the forecast of his former employer, AccuWeather.

In a blog post published in late April (Bastardi says to check for an update later this week), Bastardi mentioned the developing El Niño and high soil moisture as key factors in predicting less heat in Washington compared to last summer — bringing his views into close alignment with the Weather Service.

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But he suggested “extraordinarily” warm ocean waters near the Atlantic and Gulf coasts would probably prevent a cool summer.

Dave Tolleris

Of the outlooks reviewed, Dave Tolleris, who runs the consulting firm WxRisk, predicted the coolest temperatures. He forecasts temperatures near normal in Washington — starting cooler than normal in June, but ending with stifling heat in August.

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He sees the warm Atlantic and Gulf ocean temperatures supporting the warm conditions in the second half of the summer. But he said an active Pacific jet stream and a “parade of strong weather systems” will keep it cool early on before a “significant pattern change,” probably in July.

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The Weather Company

Of the various forecasters, Todd Crawford, chief meteorologist at the Weather Company, is predicting the hottest summer in Washington — but by a small margin. He expects the temperature to average 1.5 degrees above normal and the temperature to hit at least 90 on 45 occasions — close to predictions from AccuWeather and Joe Bastardi.

Like several other forecasters, Crawford thinks the warm Atlantic coastal waters will elevate summer temperatures. But he discounted any cooling effect El Niño might have on summer temperatures. He said it would be too weak and centered too far west to have a big effect.