In a new weekly update for pv magazine, Solcast, a DNV company, reports that clear skies driven by a persistent high-pressure system pushed May solar irradiance well above average across coastal East Asia, including Japan, Korea, eastern China, Taiwan, and the northern Philippines, with Japan seeing some of the strongest gains.
Clearer skies lifted May irradiance well above average across coastal East Asia, with Japan, Korea, eastern China, Taiwan and the northern Philippines all seeing stronger solar resource, according to analysis using the Solcast API. A persistent high was the main driver, pushing coastal irradiance above long-run May averages, while a late-month rainband reduced irradiance inland across parts of southern and central China.
Japan saw some of the strongest increases in the region. Tokyo recorded May irradiance about 15% above its 2007–2025 average, while Osaka was 14% above average, making it Osaka’s sunniest May in the Solcast record. Seoul was more modest, at 6% above average, but still sat within the broader band of unusually warm and settled conditions across Japan and the Korean Peninsula. The clear skies that cause these increases also contributed to record May heat across northern China, Mongolia and Japan, with multiple locations breaking records. High temperatures were less good news for PV operators in these regions due to efficiency decreases from the heat.
