The Omega Heatwave and Your Solar Panels

Why meteorologists called it Omega

The red warning is in. Today and tomorrow — Wednesday 24th and Thursday 25th June — the Met Office is forecasting temperatures of up to 38°C across parts of central and southern England and Wales. The June temperature record of 35.6°C, set in Southampton in 1976, is expected to break. The Wales June record of 33.7°C is also likely to fall.

Meteorologists are calling it the Omega heatwave because of the shape it makes on pressure maps: the Greek letter Ω. A ridge of high pressure is locked in place over Europe, with cooler low-pressure systems on either side that cannot shift it. Trapped Saharan air is being compressed underneath, heating further with nowhere to escape. It is the UK’s second official heatwave of 2026 — and considerably more intense than the first in May, with added humidity making it harder to recover overnight.

If you have solar panels, here is what the Omega heatwave actually means for your output.

Your panels are having their best week of the year

As temperatures started climbing earlier this week, energy think tank Ember tracked what UK residential solar was generating. On 21st and 22nd June — around the summer solstice — a typical UK rooftop solar installation produced 15 kWh per day.

That is the equivalent of five full hours of air conditioning running on free solar electricity. Across the 1.9 million UK homes with rooftop solar, that amounts to 10 million air-conditioning hours of free power every single heatwave day.

2026 is already the most productive solar year the UK has ever recorded. The half-hourly peak generation record was broken eleven times in the first half of this year alone. May 2026 set a new all-time monthly solar generation record. Then the Omega block arrived.

What the Omega block means for your panels

The same high-pressure system driving this heatwave is also keeping skies clear. No fronts pushing through, no cloud bands, no rain. The Omega block is inadvertently creating close to ideal solar irradiance conditions across England, Wales, and the Midlands.

For plug-in solar owners in London, Kent, Surrey, Hampshire, Essex, Cambridgeshire, the Midlands, and across Wales — the sun hitting your panels right now is as strong and consistent as it gets in a UK summer. Clear sky plus summer solstice irradiance is a genuinely powerful combination.

The small catch

Here is the part that does not get talked about much: solar panels are actually most efficient in cool, clear conditions — not hot ones.

The optimal panel temperature is 20–25°C. Above that, output drops by roughly 0.3% for every degree of panel surface temperature. On a hot June roof reaching 55°C in full sun, that is a real-world efficiency reduction of around 9–12% compared to a clear day in April or May.

Late spring is technically the ideal UK solar season: strong irradiance, long days, and cool air keeping panels at maximum efficiency. May 2026 proved it by setting the monthly generation record.

Why the heatwave still wins

What you lose in panel efficiency, you more than gain in daylight hours.

The summer solstice was 21st June. London has over 16 hours of daylight right now. The Omega block’s clear skies mean irradiance is high from before 5am until after 9pm. A panel running at 90% efficiency for 16 hours generates considerably more electricity than a panel at 100% efficiency running for 8.

The heat penalty is real. It just does not matter much when the sun is up for most of the day. Clear sky, Omega-block irradiance, and 16-hour summer days: your panels are generating more electricity this week than on any equivalent-brightness day in October.

Make the most of it

If you are in London, the South East, East Anglia, the Midlands, or Wales — you are in the middle of your best solar fortnight of the year.

The peak window is roughly 9am to 3pm — wider than usual because the summer sun rises high and stays there. That is when to run the big appliances:

Washing machine: before 1pm, ideally around 10–11am when irradiance peaks. Dishwasher: noon if you can manage it. EV top-up: 10am to 2pm rather than overnight. Air conditioning: the Omega heatwave is inadvertently the best possible argument for plug-in solar Britain has ever produced. Ember’s data shows your panels generating enough to run it for free for five full hours.

Your exact window

What counts is your postcode, your panel orientation, and what the cloud cover is actually doing above your specific roof — not the national average for the day. The Omega block has broadly clear skies, but there are regional variations and afternoon thunderstorm risks that can shift the numbers significantly.