100 Million Americans Under Record Heat: Why a Heat Dome Is Also a Sunburn Window
Heat domes bring stagnant, cloudless skies and brutal midday UV - extreme-heat advisories are also peak-sunburn windows.
NOAA reported that more than 100 million people across 726 US counties experienced record heat during the June 22-25, 2025 heatwave, and the contiguous US June average of 71.2 degrees F ranked seventh-warmest in 131 years.
Climate scientists at NOAA note that the clear, stagnant skies characteristic of a heat dome let abundant solar radiation reach the surface - meaning extreme-heat events typically arrive alongside elevated UV exposure.
Questions we get a lot
How many people were affected by the June 2025 heat dome?
NOAA reported that more than 100 million people across 726 US counties experienced record heat during the June 22-25, 2025 heatwave. It was one of the most widespread heat events of the season. The figures come from NOAA's monthly climate assessment.
Why is a heat dome also a high-UV risk?
Heat domes trap warm air under stagnant, largely cloudless skies, which means more solar radiation - including UV - reaches the ground around midday. So an extreme-heat advisory often coincides with peak-sunburn conditions. NOAA's data documents how intense and widespread the June 2025 event was.
How warm was June 2025 compared to past years?
The contiguous US June average reached 71.2 degrees F, ranking as the seventh-warmest June in 131 years of NOAA records. That places it firmly among the hottest on record. The reading reflects the broad scope of the late-June heat dome.
r/SkincareAddiction: 'It's a record heatwave and the sky is totally clear - do I really need to reapply sunscreen even if I'm just running errands?'