Why So Warm?

After a cooler-than-average start to June, this week brings the first burst of summer heat to the UK. The chilly northerly wind from the Arctic has been replaced by tropical maritime air from the mid-Atlantic. This change not only raises temperatures but also increases humidity, making it feel muggy during the day and uncomfortable at night. While the warmth isn’t unusual for this time of year, it has been a long time coming.

How Long Will It Last?

The heat will persist longest in England and Wales, continuing until Thursday before a cold front brings cooler air and some rain. Temperatures are expected to widely reach the mid to high 20s, with some locations possibly hitting 30°C. In Scotland and Northern Ireland, the warmest day will likely be Monday, reaching the low to mid 20s. From Tuesday onward, cloudier skies and fresher air will limit temperatures to the high teens or low 20s.

Heat-Health Alert

A yellow heat-health alert has been issued for much of England. These alerts are designed to inform the health and social care sectors that heat and humidity may impact vulnerable populations, such as the elderly, young children, and those with pre-existing health conditions. This is different from extreme heat warnings, which are issued when temperatures are expected to impact the wider population. Given this week’s typical summer heat, no extreme heat warnings are expected.

Not Always Sunny

Despite rising temperatures, it won’t be sunny all the time. In England and Wales, old weather fronts beneath the high-pressure area will cause some cloud build-up, leading to a mix of clouds and sunshine rather than clear blue skies. Scotland and Northern Ireland will see a weather front from Tuesday, bringing cloudier skies and occasional showers or rain.

Glastonbury Weather

The Glastonbury Festival kicks off later this week, and the weather can significantly impact the experience. Rain can turn the festival into a mud fest, while too much sun can cause heat-related illnesses due to the lack of shade. When I presented the weather forecast at Glastonbury in 2014, thunderstorms caused the main stages to close temporarily, but the atmosphere remained brilliant, making it my favorite outside broadcast.

This year, the weather is unlikely to cause major problems. Wednesday should be mostly dry, fine, and humid, with temperatures around 26°C, despite an isolated shower. Thursday will be cooler and fresher at 21°C, with some light rain possible. The rest of the festival should remain fine and dry with temperatures in the low 20s. However, UV and grass pollen levels will be high or very high, so don’t forget the sunscreen.