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Updated Climate Impact Company U.S. & Europe CDD Outlook

Issued: Monday June 23, 2025

Headline: U.S. & Europe JJA CDD forecasts trending hotter.

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Fig. 1: The Climate Impact Company U.S. selected cities CDD forecast for JUN-AUG and MAY-SEP compared to the last 3 years versus the 30-year normal.

Discussion: The Climate Impact Company U.S. selected cities CDD forecast for 2025 is updated (Fig. 1). The summertime (JUN/JUL/AUG) CDD outlook adjusts hotter. The national average edges upward to 113.9% of the 30-year normal as the JJA-25 forecast edges close to 2022 and 2024 summertime observations which were 3rd and 4th hottest (respectively) on record. The hottest JJA city forecasts compared to the 30-year normal in order of intensity are Seattle (132.4%), Salt Lake City (124.8%), Albany (123%), Rochester (121.3%), and Pittsburgh (120.4%). The West and Northeast have the hottest bias. The coolest (least hot) JJA forecast is Dallas (100.9%) and Kansas City (102.9%). The U.S. population weight CDD forecast projects June 2025 as the 5th hottest of this century (Table 1). However, the heat is biased away from the East-central/Mid-south U.S. mid-to-late summer forcing the population weight CDD projections to 12th to 14th hottest (nationally) of this century. The forecast trend is hotter for JUL-SEP although notable is the difference between single city forecasts vs. population weight forecasts.

JuneJulyAugustSeptember
2025265368324177
10-year252371332190
30-Year213321290155
2025 Rank

(2000-2025)

5th hottest12th hottest14th hottest14th hottest

Table 1: The Climate Impact Company U.S. selected cities CDD forecast for JUN-AUG and MAY-SEP compared to the last 3 years versus the 30-year normal.

A hotter revision for the Climate Impact Company Europe Selected Cities CDD forecast especially for western cities as the MAY-JUL projections far exceed the (warm biased) 10-year normal (Fig. 2). The AUG-SEP forecast cools to near the 10-year normal. Eastern Europe selected cities are not as boldly warm-to-hot as the western cities (Fig. 3).

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Fig 2: The Climate Impact Company Europe West selected cities CDD forecast for MAY-SEP 2025.

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Fig. 3: The Climate Impact Company Europe East selected cities CDD forecast for MAY-SEP 2025.