The complete UK heatwave preparation checklist (2026 edition)

British homes were built to trap heat, not shed it. That was fine for 1970s summers; it's a real problem when the Met Office is issuing amber heat-health alerts most Julys. The good news: most heatwave misery is avoidable with preparation that costs little or nothing. Here's the checklist we wish every UK household had.

Before the heat arrives

1. Learn your home's heat map. Spend one warm afternoon with a cheap thermometer. Which rooms cook first? South- and west-facing rooms with big glazing usually win. Those are the rooms to prioritise for shading and cooling.

2. Sort your shading now. External shading beats internal every time — the trick is stopping heat before it passes the glass. Awnings and external shutters are the gold standard; even a light-coloured sheet fixed outside a south-facing window makes a measurable difference. Inside, closed light-coloured curtains or blinds cut solar gain meaningfully; blackout linings do more.

3. Master the window rhythm. The single most effective free habit: windows shut and shaded during the day, wide open at night once outdoor temperature drops below indoor. Cross-ventilation — openings on opposite sides of the home — can flush an astonishing amount of heat overnight.

4. Service your fans (and place them right). A fan pointed out of a hot window in the evening pushes hot air out; another drawing cooler air in from a shaded side speeds the exchange. During peak heat, a fan over a bowl of ice water is a genuinely useful stopgap for one person — but note fans stop helping much above ~35°C and can worsen dehydration.

5. Check who's vulnerable. Over-65s, babies, and anyone with heart, respiratory or kidney conditions or taking certain medications (diuretics, some antidepressants and antihistamines) need cooler rooms. If that's your household, treat proper cooling as health equipment, not luxury — and don't leave sourcing it until the alert lands.

6. Insulation works both ways. Loft insulation slows heat coming down in summer as well as up in winter. If your loft's under-insulated, fixing it is a year-round win.

7. Kill indoor heat sources. Ovens, tumble dryers, gaming PCs and even incandescent-era lighting add real heat. Plan cold meals, line-dry, and shift heavy appliance use to late evening during hot spells.

Deciding on active cooling

8. Size before you shop. Cooling capacity is measured in BTU (or kW). Too small never cools; too big cycles badly and dehumidifies poorly. A typical UK double bedroom needs roughly 9,000 BTU (~2.6 kW); big open-plan spaces need far more. Our free calculator does this in a minute — it's an estimate, not a survey, but it stops you buying blind.

9. Portable vs installed vs rental. Portables arrive fast, need no permission, and follow you when you move — at the cost of some noise and a hose out the window. Installed splits are quieter, far more efficient, and heat in winter too — but need certified installation and sometimes permissions. Rental suits short, sharp needs. Full comparison here.

10. Buy before the rush — or reserve. The pattern repeats every summer: the first amber alert empties shelves of every decent unit within days, and installer diaries fill for weeks. Whatever you choose, decide before the forecast turns red. (That's the entire reason Coolhaven priority reservations exist — £10, refundable, and you're ahead of the rush.)

During the heatwave

11. Hydrate on schedule, not thirst. By the time you're thirsty you're behind. Urine colour is the honest gauge.

12. Cool the person, not just the room. Cold water on wrists and neck, cool showers, damp sheets — they buy comfort cheaply when the mercury peaks.

13. Close the loop at night. Bedroom below ~24°C makes sleep dramatically better. Run cooling to pre-chill the bedroom an hour before bed rather than fighting heat at 2am.

14. Check on neighbours. Heat kills quietly, mostly older people living alone. A knock on the door during an amber alert is a small act that genuinely saves lives.

Preparing early isn't paranoia — it's how you make a heatwave boring. That's the goal.