Dry August pushes Dallas soiling losses towards 2% as North American GHI diverges

A dry August split the country's solar weather into two extremes. Sunlight levels, measured as global horizontal irradiance (GHI, the total sunlight hitting a flat surface), dropped sharply across the Upper Midwest and Great Lakes, where Indiana and Ohio had their wettest August on record. Chicago, Toronto, and Buffalo all saw well-below-normal sun. Meanwhile, Texas, Oklahoma, the Pacific Northwest, and Mexico got more sun than usual, with Texas and Oklahoma logging one of their five driest Augusts on record. Wildfire smoke in the Northwest and British Columbia also cut into sunlight there by 1-2%.

For homeowners with solar panels near Dallas, the dry stretch had a downside: without rain to wash dust and debris off panels, modeled energy loss from dirty panels climbed toward 2% by the end of August, the highest late-August figure seen since 2007. The whole June-through-August stretch ranked as the second-dirtiest summer on record for the area, even though June started out clean thanks to frequent rain. If you own panels in a region that's gone unusually dry, this is a reminder that lack of rain, not just pollution or dust storms, can quietly reduce how much power your system produces.

Hawaii also had a rough month weather-wise: Hurricane Lala made the islands' first direct hurricane landfall since 1992, bringing 90 mph winds, over 30 inches of rain, and widespread power outages. Despite the storm, monthly sunlight there ended up only 4% below normal since the flooding was brief.