Southeast Asia surged under clear skies while Japan’s storms capped solar gains

<p>Extreme pre-monsoon heat and an unusually dry atmosphere lifted irradiance well above average across mainland and maritime Southeast Asia, while the fading La Niña reduced convective cloud across much of the western Pacific, according to analysis using the <a href="https://solcast.com/?utm_source=pvmag&amp;utm_medium=Content&amp;utm_campaign=ghimap">Solcast API</a>. Southern China broadly extended its above-normal run for 2026, though the Yangtze Delta lagged as cloud and rain impacted solar production. Japan and South Korea stood apart, with storms and elevated moisture keeping irradiance close to, or slightly below, normal despite warm temperatures.</p>

<figure class="wp-block-image size-large"><img alt="" class="wp-image-136041" height="1024" src="https://www.pv-magazine.com/wp-content/uploads/2026/05/GHI-Deviation-Asia-Apr2026-841x1024.png" width="841" /></figure>

<p>Across mainland Southeast Asia, persistent heatwave conditions were the dominant driver. The region averaged around 10% above the 2007–2025 irradiance baseline, with roughly 95% of locations exceeding normal levels. Bangkok recorded its sunniest April in the 20-year Solcast API data record, finishing 14.5% above the historical mean and well ahead of any previous year.</p>

<figure class="wp-block-image size-large"><img alt="" class="wp-image-136042" height="820" src="https://www.pv-magazine.com/wp-content/uploads/2026/05/Bangkok-Thailand-April-2026-GHI-Profile-1024x820.png" width="1024" /></figure>

<p>Daily maximum temperatures of 36–39 C were widespread from Bangkok and Phnom Penh through to Vientiane and Ho Chi Minh City. Single-day GHI plot from 8–12 April show near-continuous clear skies across the mainland. Imagery from 9 April showed twin<br />tropical cyclones, Maila and Sinlaku, active simultaneously over the western Pacific while mainland Southeast Asia remained almost entirely cloud-free under persistent heatwave conditions.</p>

<figure class="wp-block-image size-large"><img alt="" class="wp-image-136043" height="889" src="https://www.pv-magazine.com/wp-content/uploads/2026/05/April-9-1024x889.png" width="1024" /></figure>

<p>Humidity was around 9% below the April long-term average and rainfall averaged 1.7 mm/day below normal, sharply reducing cloud formation. These conditions were flagged by regional meteorological agencies as “extreme hot conditions” and coincided with a period in which several countries struggled to meet surging cooling demand, highlighting the disconnect between abundant sunlight and constrained conventional energy supply. </p>

<p>Maritime Southeast Asia saw a similarly strong outcome as La Niña faded toward ENSO-neutral conditions. Indonesia and the Philippines averaged around 9% above normal for April, with 97% of the maritime region recording positive anomalies. Jakarta<br />finished 7.5% above its long-term mean, its third sunniest April on record. Precipitation across the Maritime Continent was nearly 2 mm/day below the April long-term average. </p>

<p>The pattern aligns with the broader ENSO transition noted in early April, with NOAA’s Climate Prediction Center issuing a Final La Niña advisory on April 9 as suppressed convection persisted over western Indonesia and reduced tropical moisture transport across the equatorial western Pacific. While twin tropical cyclones, Maila and Sinlaku, developed to the east during the month, mainland and much of maritime Southeast Asia remained under predominantly clear conditions.</p>

<figure class="wp-block-image size-large"><img alt="" class="wp-image-136044" height="1024" src="https://www.pv-magazine.com/wp-content/uploads/2026/05/Average-Daily-GHI-Asia-Apr20261-841x1024.png" width="841" /></figure>

<p>In China, southern coastal provinces continued a run of above-average months in 2026. Guangdong and Fujian finished around 6% above normal, even as torrential late-month rainfall exceeding 100–200 mm triggered flood preparations. The Yangtze Delta recorded the most significant irradiance deficit of the month, with persistent cloud and rain leaving GHI around 10% below the long-term average between Shanghai and Nanjing. April marks the beginning of the rainy season across central and southern China, and the late-month flooding may be an early indication of a stronger wet season ahead if El Niño conditions develop later this year, as forecast.</p>

<figure class="wp-block-image size-large"><img alt="" class="wp-image-136045" height="782" src="https://www.pv-magazine.com/wp-content/uploads/2026/05/Fukuoka-Japan-April-2026-GHI-Profile-1024x782.png" width="1024" /></figure>

<p>Further northeast, below-average conditions extended into southern Japan and Jeju, where irradiance deficits reached approximately 11%. Northern Japan and much of mainland South Korea performed better, finishing near or slightly above average overall, but repeated storm systems prevented the broader region from sharing in the significant irradiance gains seen farther south.</p>

<p><em><a href="https://solcast.com/?utm_source=pvmag&amp;utm_medium=Content&amp;utm_campaign=ghimap" rel="noreferrer noopener" target="_blank">Solcast</a> produces these figures by tracking clouds and aerosols at 1-2km resolution globally, using satellite data and proprietary <a href="https://solcast.com/irradiance-data-methodology/?utm_source=pvmag&amp;utm_medium=Content&amp;utm_campaign=ghimap" rel="noreferrer noopener" target="_blank">AI/ML algorithms</a>. This data is used to drive irradiance models, enabling Solcast to calculate irradiance at high resolution, with typical bias of less than 2%, and also cloud-tracking forecasts. This data is used by more than 350 companies managing over 300 GW of solar assets globally.</em></p>
<p>The post <a href="https://www.pv-magazine.com/2026/05/29/southeast-asia-surged-under-clear-skies-while-japans-storms-capped-solar-gains/">Southeast Asia surged under clear skies while Japan’s storms capped solar gains</a> appeared first on <a href="https://www.pv-magazine.com">pv magazine Global</a>.</p>