Europe's August solar irradiance surplus
Analysis from Solcast shows Europe's solar irradiance averaged 5% above the long-term norm in August 2026, with nearly three-quarters of the continent
Europe's solar irradiance averaged 5% above the 2007-2025 norm in August 2026. This data, from Solcast, a DNV company, extends a period of elevated solar resource recorded during June and July.
Nearly three-quarters of the continent received above-average irradiance. Persistent high pressure limited cloud formation and storm development for much of the month.
High Pressure Drives Sunny Conditions
High pressure remained the dominant influence. Sinking air within this persistent system stabilised the atmosphere, supporting extended clear sky periods. Although August is typically Europe's second-sunniest month, some regions saw irradiance more than 20% above the seasonal norm. Southern England experienced the continent's strongest positive anomalies.
This marked a third consecutive month of elevated solar resource across much of western and central Europe. London's cumulative global horizontal irradiance reached a record high for this point in the year.
The sunny conditions coincided with exceptional drought. Southern England experienced 62 consecutive dry days through mid-August, breaking a previous record of 51 days. According to the European Commission's Joint Research Centre, critically low water levels on the Rhine and Danube rivers disrupted hydropower and nuclear generation. This increased reliance on other sources, including solar power.
In Birmingham, the prolonged dry spell provided few opportunities for natural rainfall to clean solar modules. Modelled soiling losses were allowed to accumulate before rain returned in the middle of the month.
Late-August Weather Shift
The prolonged high-pressure pattern began to break down in the second half of August. As the system weakened and shifted eastward, a cold front arrived from the Atlantic. Temperatures fell by more than 15 degrees Celsius across parts of western Europe after weeks of persistent heat.
Increasing cloud and rainfall reduced the earlier irradiance surplus as the front moved into France and Germany. The change had an uneven effect across the continent.
Central and eastern regions retained more of their earlier surplus. Parts of southwestern Europe, however, finished the month closer to or below their long-term average. Daily irradiance profiles for Porto show the shift clearly. Early-month profiles were consistent, while several days around and after mid-month recorded pronounced daytime reductions.
Solcast produces its figures by tracking clouds and aerosols at a 1-2km resolution globally. The company uses satellite data and proprietary AI and machine learning algorithms. This data drives irradiance models, enabling high-resolution calculations with a typical bias of less than 2%. More than 350 companies managing over 350 GW of global solar assets use this data.
