Southeast Asia is forecast to see the strongest positive solar resource anomaly in the second half of 2026, according to analysis using the Solcast API, as a strengthening El Niño and unusually warm oceans shift cloud and rainfall patterns across the tropics. The analysis of seasonal forecast models also points to above-normal irradiance in Europe, northern South America and eastern Australia, while parts of higher-latitude South America and North America remain more uncertain.
The projection is built by comparing seasonal forecasts for the final six months of 2026 from four major meteorological centres: the European Centre for Medium-Range Weather Forecasts (ECMWF), the UK Met Office (UKMO), the Japan Meteorological Agency (JMA), and the US National Centers for Environmental Prediction (NCEP). Comparing them shows where the models agree and where the outlook is less certain. Southeast Asia shows the strongest model agreement, with all four forecasts pointing to above-normal irradiance. Positive irradiance anomalies also appear across parts of the tropics, including Africa and northern South America. Higher-latitude areas of both continents are forecast to be cloudier. Most models place central and western Europe above the long-term average for irradiance, with India also forecast to finish above normal. North America is where the models diverge most.
The model comparison highlights where the forecast is most robust: agreement is strongest across Southeast Asia, while North America shows greater spread between models.
El Niño is a recurring climate pattern in which the tropical Pacific Ocean becomes warmer than usual, shifting weather across large parts of the globe. There is strong agreement that it will intensify into a strong to very strong event by late 2026, alongside high sea surface temperatures across the globe. Monthly global horizontal irradiance (GHI) forecasts suggest that most regional anomalies persist through October, before the forecast pattern becomes more variable in November and December. China and the United States are the exceptions, with more month-to-month variability expected.
The monthly GHI outlook shows whether anomalies are persistent or transitional. In most regions, the sign of the anomaly remains broadly stable into October before more substantial shifts appear late in the year.
Combining these forecasts with Solcast’s analysis of the first half of 2026 gives a view of how the year may end, though forecast uncertainty means early-year trends dominate in some regions. The year-end map combines the irradiance already observed over the first half of 2026 with the second-half forecast, showing how the full year is shaping up region by region.
The year-end map combines the irradiance already observed over the first half of 2026 with the second-half forecast, showing how the full year is shaping up region by region.
Europe’s positive first-half anomaly is forecast to persist into year end, particularly across central and western areas, with some areas finishing around 5% above normal. The outlook suggests reduced cloud cover is likely to maintain above-normal irradiance, rather than a late-year reversal of the early gains. Paris illustrates the pattern, its cumulative irradiance for 2026 tracking toward the upper end of the historical range.
In the United States, reductions near the northern and southern margins contrast with stronger irradiance through parts of the central US, making the national picture positive overall but regionally uneven. Houston, near the southern border, begins strong, but end slightly lower than the average.
In Australia, the above-normal signal sits along the east and west coasts, while the centre of the country is forecast slightly below average. Northern South America is expected to end above normal, while the south, despite a sunny start, is projected to finish below average. São Paulo in the south is an example of this lower than average trend.
Across Asia, the clearest second-half anomaly is in Southeast Asia, where the models agree on above-normal irradiance. Coastal Asia, which was above normal earlier in the year, is forecast to move closer to the long-term average, suggesting the regional pattern becomes more concentrated in the tropics rather than remaining broadly coastal. Singapore shows the effect at a single site, its cumulative irradiance for 2026 sitting toward the top of the historical range.
Solcast produces these figures by tracking clouds and aerosols at 1-2km resolution globally, using satellite data and proprietary AI/ML algorithms. 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.
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