From first-half extremes to El Niño: the outlook for global solar resource in 2026

Solar resource shifted markedly across major markets during the first half of 2026. With El Niño strengthening, seasonal forecasts now indicate where those patterns may persist, reverse or become more uncertain through year end.

Global solar resource was redistributed during the first half of 2026 as atmospheric blocking, disruption to the polar vortex and extreme weather changed cloud, rainfall and aerosol patterns across major solar markets. From April, developing El Niño conditions began to exert a growing influence, setting the stage for further changes during the second half of the year.

Analysis using the Solcast API shows that much of Europe, the United States, Southeast Asia, South America and Central Africa recorded irradiance between 5% and 10% above the long-term average during the first six months of the year. Most of Canada, Mexico, South Africa, North Africa, parts of western Russia and Central Asia were between 5% and 10% below average.

These regional contrasts are visible in the first-half anomaly map, which compares January–June GHI with the 2007–2025 average. Above-normal irradiance extended across much of Europe and the United States, while deficits developed across Canada, Mexico and parts of Africa and Asia.

 
The outlook for the final six months of 2026 is based on seasonal forecasts 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 the models shows where there is broad agreement and where the outlook remains more uncertain.

The four forecasts reveal both the common signals and the limits of the outlook. Agreement is strongest where similar positive or negative anomalies appear across all four panels.

 
The strongest agreement is across Southeast Asia, where all four models point to above-normal irradiance. Positive anomalies are also forecast across Europe, northern South America and parts of eastern and western Australia. The models diverge most over North America, while higher-latitude areas of North and South America face a less certain or more negative outlook.

Europe’s first-half gains are likely to persist

Most of Europe received significantly more solar resource than normal during the first half of 2026. The pattern began in winter, when cold, dry air reduced cloud cover across parts of eastern and northern Europe, raising irradiance even as storm systems reduced solar resource farther west.

The effect was widespread by the end of June. Comparing first-half GHI with the historical average shows the strongest uplift extending across western and central Europe, with above-average irradiance also reaching parts of northern Europe.

Persistent high pressure over the North Sea reinforced this pattern in April, keeping skies clearer across western and northern Europe. France recorded irradiance 13% above the 2007–2025 baseline, Germany was 11% above average and Finland was 16% above.

Clearer conditions extended from Spain to Ukraine during May. The strongest anomalies were centred around Austria, where irradiance reached as much as 25% above normal. These conditions produced extended periods of stronger irradiance across several major European markets, despite local reductions around the edges of the weather systems.

Lyon illustrates how Europe’s clearer conditions accumulated over time. Its year-to-date GHI remained above the historical average through the first half, reaching 13.3% above average by the end of June.

Europe’s broader irradiance uplift continued despite a Saharan dust event affecting southern Europe in March. The map shows the geographic extent of the transported dust; although its influence on the regional irradiance pattern was limited, deposition can increase soiling and affect module-cleaning schedules.

 
Europe’s positive first-half anomaly is forecast to persist through the remainder of the year, particularly across central and western areas. Most of the seasonal models place these regions above the long-term average, with some areas expected to finish 2026 around 5% above normal.

The outlook suggests that these gains will persist rather than reverse during the second half. Paris provides one example: after tracking 10.6% above average at mid-year, the four seasonal models indicate that annual GHI could finish approximately 6–8% above average.

An uneven outlook follows North America’s early gains

North America’s first-half pattern was more varied. The United States experienced repeated periods of above-average irradiance during winter and early spring, after storms in late January gave way to clearer conditions across large parts of the central, eastern, southern and western states.

The North American pattern changed substantially between the first and second quarters. Winter and early-spring gains extended across much of the United States, before increasing cloud reduced irradiance across the south during April–June, particularly around Texas and the Gulf Coast.

Conditions changed during the second quarter. Western and interior markets remained near or above average, while Texas and the Gulf Coast moved below normal as moisture, cloud and rainfall reduced irradiance. The gains accumulated earlier in the year were therefore partly offset during spring.

Dallas shows how this shift narrowed the early-year surplus. Cumulative GHI remained slightly above average at mid-year, but the margin had fallen to around 1% as cloud and rainfall reduced the gains accumulated earlier in 2026.

California’s Central Valley was one notable exception to the broader pattern across the United States. Persistent tule fog suppressed solar resource during extended periods, with the change visible in a comparison of first- and second-quarter conditions.

The regional variation observed during the first half is expected to continue. However, the outlook for North America is less certain than for the other regions, with the four seasonal forecasting systems disagreeing over both the location and direction of irradiance anomalies.

Current forecasts show lower irradiance near the northern and southern margins of the United States, contrasting with stronger irradiance across parts of the central states. This would leave the national picture positive overall but regionally uneven.

Houston, near the southern edge of this pattern, began the year strongly but is forecast to finish slightly below its long-term average. Cloudier conditions during the second half could offset some of its earlier gains.

 
South America’s irradiance divide is forecast to reverse

South America recorded contrasting conditions during the first half of the year. Northern regions experienced irradiance reductions of up to 15% during January as increased rainfall and storm activity produced more cloud cover. Farther south, hotter and drier conditions across northern Argentina and central Chile reduced cloud formation and raised irradiance in some areas.

By the end of June, these changing conditions had produced a fragmented continental pattern. Above-average GHI covered much of Brazil and parts of the west coast, while deficits remained across several northern and southern areas.

Comparing observed GHI with clear-sky GHI helps separate the influence of cloud from that of aerosols. In January, parts of southern South America had relatively clear conditions, but wildfire smoke limited the corresponding increase in irradiance reaching the surface.

The second-half forecast points to a reversal of the regional divide. Northern South America is expected to finish the year above normal, supported by positive irradiance anomalies across parts of the tropics. Higher-latitude areas of the continent, however, are forecast to become cloudier.

São Paulo illustrates how the southern outlook could weaken the annual result. It was tracking 1.4% below average at mid-year, and the models forecast that annual GHI will finish approximately 1.4–3.5% below average.

Southeast Asia emerges from a shifting first-half pattern

Asia did not follow a single regional pattern during the first half of 2026. Instead, the strongest irradiance anomalies shifted between coastal East Asia and markets farther south as cloud and rainfall patterns changed.

The resulting first-half map contains no single north–south divide. Stronger GHI across parts of China and mainland Southeast Asia sits alongside localised deficits, reflecting how repeatedly the regional pattern shifted.

 
Southern and coastal China began the year strongly. Reduced cloud cover and lower aerosol levels raised irradiance during January and February, with Hong Kong recording irradiance more than 25% above average in January. Parts of southern China and Taiwan remained above average during February.

Hong Kong shows how strongly the early gains accumulated before conditions became more variable. Its year-to-date GHI remained 5.4% above average at the end of June, despite shifts in cloud and rainfall later in the period.

By April, the strongest gains had shifted south into mainland Southeast Asia. Clearer and drier conditions raised irradiance, and Bangkok recorded its sunniest April since 2007. At the same time, persistent cloud and rainfall reduced irradiance across eastern China, with the Yangtze River Delta around 10% below average.

The monthly comparison reveals how quickly those contrasts changed. Singapore, Tokyo, Chongqing and Shanghai moved between positive and negative anomalies at different points, illustrating why the first-half Asian pattern cannot be reduced to a single regional trend.

Despite this first-half variability, the second-half forecasts show a much clearer regional signal. Southeast Asia has the strongest positive outlook for the final six months of 2026, with all four seasonal forecasting systems pointing to above-normal irradiance.

The outlook is consistent with a strengthening El Niño, which is expected to alter rainfall and cloud patterns across the tropical Pacific and surrounding regions. The models broadly agree that El Niño will intensify into a strong to very strong event by late 2026, alongside unusually high global sea-surface temperatures.

Coastal Asia, which recorded above-normal irradiance earlier in the year, is forecast to move closer to its long-term average. The positive regional anomaly is therefore expected to become more concentrated in Southeast Asia rather than remaining broadly distributed along the Asian coast.

Singapore illustrates the stronger outlook for Southeast Asia. It was tracking 4.7% above average at mid-year, and the four models suggest that annual GHI will finish approximately 4.1–6.4% above average. 

Australia’s coastal–inland divide is set to continue

Australia experienced a clear contrast between inland and coastal regions during the first half of the year. Central Australia recorded below-average irradiance, while parts of the east and west coasts received stronger solar resource.

Australia’s first-half pattern divided the country between inland deficits and stronger coastal irradiance. Compared with the historical average, central areas finished below normal while parts of the east and west coasts recorded above-average GHI.

 
Northern and inland Australia experienced repeated periods of cloud and rainfall during the first half of 2026, including several monsoonal and tropical cyclone events. January was mostly above average, although monsoonal cloud and Tropical Cyclone Koji reduced irradiance in the tropical north.

Cyclone Mitchell contributed to Australia’s wettest February since 2011, while Cyclones Narelle and Malia brought further periods of cloud and rainfall across parts of Queensland, the Northern Territory and Western Australia. Together, these systems contributed to a cloudier and wetter first half across parts of northern Australia.

Darwin illustrates how these conditions affected cumulative solar resource over time. After beginning the year near average, repeated periods of cloud and rainfall pushed cumulative GHI below the historical range, reaching 4.6% below average by the end of June.

For solar operators in affected inland and northern regions, the conditions resulted in more variable irradiance, greater soiling risk from dust and more challenging site conditions during periods of heavy rainfall and cyclone activity. Parts of the east and west coasts received stronger solar resource during more frequent clear periods.

This coastal–inland contrast is expected to continue during the second half of the year. Seasonal forecasts place above-normal irradiance along parts of the east and west coasts, while central Australia is expected to remain slightly below average.

El Niño typically changes rainfall and cloud patterns across Australia, although its effects vary by location and season. Its expected strengthening during the second half adds to the likelihood of continued regional differences rather than a uniform national pattern.

El Niño reinforces regional contrasts through year end

Several forecast anomalies remain broadly consistent through October, before the regional pattern becomes more variable during November and December. The combined monthly outlook shows how these signals develop, with China and the United States displaying greater month-to-month variability than most other regions.

 
Averaging the July–December forecast provides a clearer view of the expected second-half pattern. The map highlights the positive outlook across Southeast Asia and parts of Europe and Australia, while also showing weaker signals across higher-latitude areas of the Americas.

Europe’s early gains are expected to persist, particularly across central and western areas. Southeast Asia is forecast to move further above normal, while northern South America is also likely to finish the year positively.

The United States is expected to remain above average overall, although that national result masks differences between the central states and the country’s northern and southern margins. Australia is likely to retain its coastal–inland contrast, while southern South America may finish below average despite stronger irradiance earlier in the year.

Seasonal forecasts carry greater uncertainty at longer lead times, particularly in regions where the models disagree. They are therefore best interpreted as an indication of the direction and persistence of regional anomalies, rather than as precise predictions for individual sites.

Conclusion

Large-scale changes in cloud and rainfall were the main drivers of global solar-resource anomalies during the first half of 2026. These produced sustained solar gains across much of Europe and the United States, alongside more variable outcomes in Asia, South America and Australia.

Localised events, including tropical cyclones, dust and wildfire smoke, did not determine the broader global pattern. Their shorter-term effects may nevertheless be relevant to site operations, including production variability, soiling, cleaning schedules and equipment maintenance.

A strengthening El Niño is expected to play a greater role during the second half of the year, particularly across the tropics. The forecasts provide the clearest signal where models agree, led by the positive outlook for Southeast Asia. In regions such as North America, where the models diverge, updated seasonal guidance and shorter-term forecasts will remain important for operational planning.

7/27/2026 12:00:00 PM