A post-heatwave cool-down has driven the spiders indoors, with experts citing warmer spells boosting breeding and NHS data showing bite-related hospital admissions doubled
Britain is bracing for a fresh wave of spider sightings after record May heat followed by a sharp cool-down, with experts warning the arachnids are being driven indoors through tiny gaps around doors, windows and air bricks. Moreover, UK searches for “how to identify a false widow spider” have surged by 5,000% this week.
Additionally, NHS figures show hospital admissions linked to spider bites have more than doubled over the past decade. Some experts say warm spells can supercharge breeding outdoors, before cooler nights send them scrambling for sheltered, warmer spaces inside our homes.
Now, garden expert Luke Newnes explains what is driving the sudden spike and three quick ways homeowners can stop the spiders getting indoors.
After Britain endured one of its hottest spells of the year, with two consecutive days in May breaking temperature records, the sudden cool-down is now driving a wave of false widow spider sightings across the UK. NHS figures obtained through a Freedom of Information request earlier this year revealed that 100 people required hospital treatment following spider bites in 2025, which is double the 47 cases recorded a decade ago.
Oxford University ecologist Clive Hambler, who has described the noble false widow as “the most dangerous spider currently breeding in Britain”, warned: “The days when you could just treat spiders as benign in Britain are over”. Experts say the spike in sightings are due to prolonged heatwaves that accelerates breeding in outdoor habitats.
When the temperature suddenly drops, booming spider populations begin forcing their way indoors, squeezing through gaps around window frames, door seals and air bricks in search of warmth. Luke Newnes, garden expert at Hillarys, said: “A sustained hot spell is good news for false widows – warm conditions speed up breeding and push population numbers higher than normal.
“The cool-down afterwards is what sends them inside. They are not aggressive and they are not hunting people out, but they will move through any gap they can find in a door threshold or window seal.
“The entry points are the thing to focus on, and most UK homes have not had those checked in years.”
Where false widows are hiding around your home right now:
Ivy and climbing plants against walls: Dense growth holds warmth, provides insect prey and sits directly against the brickwork – giving spiders a covered route straight to gaps around window frames.
Window and door frames: Perished silicone and worn threshold seals are the most common entry points. False widows build webs in the corners of frames and in any gap between frame and brickwork.
Garden sheds and outbuildings: Undisturbed and warm, sheds harbour large numbers of false widows over summer. They are a primary reservoir for indoor invasions as temperatures fall.
Soffits and fascia boards: Cracked boards and unscreened roof vents give direct access to loft voids, where spiders can go undetected for months.
Behind outdoor plant pots and garden furniture: Items stored against external walls create a sheltered corridor to entry points. Moving them away from the house removes that bridge.
Three quick fixes to stop them getting in
Check and reseal window and door frame: Exterior-grade silicone shrinks and cracks over time. Any gap you can press a fingernail into is wide enough for a false widow. A tube costs around £5 and takes 20 minutes to apply.
Replace worn threshold seals and draught brushes: The gap at the base of a back or side door is one of the most overlooked entry points. Brush strips cost under £10 from most hardware stores.
Cut back ivy and climbing plants touching the house: Cutting back by 30cm from the wall removes the bridge between garden populations and gaps around frames, without harming the plant.
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