UK households urged 'do not leave windows open' this week as wasp swarm imminent

Pest experts say the UK is about to face one of its worst wasp seasons in years, with swarms expected in the heatwave from today until the end of the month. One UK-based pest control company reports a 618 percent surge in wasp call-outs in June 2025 compared to last year and august expected to be higher.

This week swathes of the UK are braced for our fourth heatwave - after two in June and one in July - with the mercury set to peak in the mid-30s in London on Tuesday. Now a scientist fears a warm, wet spring, 2025 will mean the swarms this week will be worse than ever - and coincide with Brits leaving their windows open to handle the new heat surge.

Dr Nathaniel Green, an insect behaviour specialist, warned: "We're seeing nests far larger than normal, which means more wasps and more aggression.

"Keep your windows shut - otherwise you're giving them an open invitation into your home."

Why dirty windows are a wasp magnet:

It's not just food scraps or sweet drinks that lure them in. Dirty windows could be the real problem.

Dr Green adds: "Smears, pollen, dust - these are like signposts for insects.

"And to a wasp, a grimy window can signal a safe, undisturbed place to build a nest. If your windows are filthy, you're telling them: 'Nobody's home - set up camp here'."

That's bad news for anyone - but it's especially dangerous for people allergic to wasp stings. A single sting can cause swelling, hives, dizziness, and in severe cases, anaphylaxis, which can be fatal if not treated immediately.

In the UK, there are between two and nine deaths from wasp stings every year, with wasp stings responsible for twice as many anaphylaxis deaths as bee stings, according to the NHS's National Institute for Health and Care Excellence (NICE).

Dr Green goes on: "Wasps don't just sting once and fly away.

"If they feel threatened, they can sting repeatedly, and that venom can be deadly for someone with an allergy. In a swarm, the danger multiplies."

How to keep them away:

Window sticker experts at Quote My Wall have learned plenty of window-cleaning tricks over the years, as spotless glass is essential before any application of stickers.

Here are their top three tips to make your windows less inviting to wasps:

1. Choose the right cleaner - A mix of white vinegar and water (50/50) or a good quality glass cleaner will strip away pollen and organic residue.

2. Ditch paper towels - Use microfibre cloths to trap dust and avoid streaks. A truly clean finish leaves nothing for wasps to sniff out.

3. Clean on a cloudy day - Direct sunlight dries cleaner too quickly, leaving streaks and smears that can still attract pests.

Shut the windows - all month:

Dr Green's message is clear: keep your windows shut for the rest of August.

Afternoons are peak activity time, and with this year's early surge, expect more aggressive colonies. "If you don't want a wasp flying into your lounge - or worse, starting a nest nearby - clean your windows and keep them closed," he warns.

The swarms won't last forever, but even a few weeks can feel like a siege so better to be safe - and sting-free - than sorry.