Despite record U.S. heat in July, North American irradiance remains near average

July 2026 was the hottest month ever recorded in the United States, according to federal climate data, with both the highest average temperatures and the warmest overnight lows on record. Despite that heat, sunshine levels across North America stayed close to normal. Solar irradiance, the amount of sunlight reaching the ground, which determines how much power rooftop panels can produce, was within 5% of the long-term average across three-quarters of the continent, according to satellite-based tracking from Solcast.

The reason heat and sunshine did not move together comes down to smoke and clouds. Wildfire smoke over the Pacific Northwest scattered and absorbed sunlight during the second half of July, cutting into solar output there and adding haze that can also dirty panels. Meanwhile, heavy rain events in Texas and the Northeast brought thick storm cloud that suppressed sunshine in those areas too. Knippa, Texas, saw over 700 mm of rain in a five-day span in mid-July, and parts of eastern New York got up to 300 mm over two days at the end of the month. Both regions ranked among the areas with the lowest sunlight levels for the month. At the same time, the heat drove record electricity demand in Texas, with the state's grid operator logging its highest-ever peak load on July 22.

For homeowners with solar panels, the takeaway is that a record-hot month does not automatically mean record solar output. Local smoke, haze, and storm clouds can hold back generation even during an otherwise sunny stretch, and where you live matters more than the national heat headlines suggest.