The Anomalous Summer Playbook: When Heat Stays Longer Than Normal
Two-week heatwaves used to be rare in Europe. They are now routine. The household that prepares in March handles a six-week scorching summer fundamentally differently from the one that improvises in July. Six small actions, none of them expensive.
The pattern most Europeans haven't adjusted to
Until roughly 2018, a serious European heatwave was a 3–7 day event that came once every few years. Since 2018, the pattern has shifted: multiple heatwaves per summer, each lasting longer, with overnight low temperatures (the dangerous part) remaining elevated for weeks at a time. The 2003, 2015, 2018, 2022, 2023 and 2024 summers all broke records in different parts of Europe; the trend is unambiguous in the Copernicus Climate Change Service data.
The household preparation that worked for 5-day heatwaves does not work for 6-week ones. What changes is not the intensity but the duration: ventilation, food storage, sleep, medication, and water all degrade differently when the heat is sustained.
Action 1 — March: identify your cool room properly
Walk through your home. Find the room that stays coolest during the hottest hour of the previous summer. Usually it is the lowest, most internal, least sun-facing room. Verify by leaving a cheap thermometer there for a week — guesses are often wrong. This is your daytime base when temperatures climb above 32°C.
If you live in a top-floor flat with no internal rooms, the honest answer is that your dwelling becomes dangerous above ~35°C ambient. Plan for that: where can you spend the hot 4 hours of the day? A library, a shopping centre, a relative's ground-floor flat. The plan is to leave, not to suffer.
Action 2 — April: solar gain mitigation
External shade keeps far more heat out than internal blinds — sunlight must be stopped before it passes the glass. Order external blinds, awnings, or even cheap shade-cloth for south- and west-facing windows now. Installing in March costs half what installing in July costs (the trade is busy and prices rise). A €60 shade-cloth on the largest window pays back in one weekend of comfort.
For renters: aluminium-foil window film (€15) reflects much of the incoming solar radiation. Cuts the room temperature by 3–4°C in direct-sun rooms. Removes without residue. Allowed under almost every tenancy agreement.
Action 3 — May: water-storage upgrade
Sustained heat doubles drinking-water needs. A normal household reserve of 30 litres is too little for a week-long heatwave with four people. Aim for 6 litres/person/day stored — for a family of four, that is roughly 24 large bottles or 4 jerry cans.
Mediterranean households should add a 20-litre buffer for emergency hygiene: in a sustained drought with rationing, washing hands properly becomes scarce, and gastrointestinal illness rates rise sharply. Cheap insurance.
Action 4 — May: review medication storage
Many common medications degrade above 25°C. Insulin (unopened, room temperature): about 28 days at <30°C, less at higher temperatures. GLP-1 medications (Ozempic-type): refrigerated only — a power cut during a heatwave is the worst-case scenario, plan a fallback. EpiPens, antibiotics, blood-pressure tablets, and most heart medications: store in the coolest room, ideally on the floor of a cupboard against an interior wall.
For households with a member on critical medication: a 60-day buffer instead of the usual 30-day buffer. Pharmacies struggle during heatwaves with both supply disruptions and increased demand from heat-related conditions.
Action 5 — June: routine adjustments for the household
Decide before the heatwave hits. Two adjustments matter most:
- Shift activity to morning. Anything physical — shopping, exercise, household tasks — moves to before 11am or after 8pm. This is a household norm, not a personal choice; it works when everyone agrees in advance.
- Sleep arrangement. If your bedroom is the warmest room (often, because of west-facing windows or top floor), prepare a sleep alternative in your cool room. A futon, an air mattress, a sleeping bag — anything to make the cool room sleepable for the week-long stretches when the bedroom is unbearable.
Action 6 — July: who is at acute risk in your circle
This is the action most preparedness writing misses. By July, you should know which 2–3 elderly or chronically ill people in your immediate area would not handle a heatwave well. Not as a database — as a quiet awareness, plus their phone numbers. During a multi-day 38°C event in 2003, the people who died in France were largely elderly and alone; the people who survived were the ones whose neighbours checked on them. This was the only systematic finding of the post-event review.
The check-in itself is short: knock at 10am with a cold bottle of water and ten minutes of conversation. Do not lecture. Do not call the situation an emergency. Do confirm they have water, are eating, are taking medication.
What the playbook isn't
This is not air-conditioning advocacy. AC works but generates massive electricity demand, and during the worst heatwaves the grid is already at maximum load — the most affected places are also where AC fails. The playbook above keeps you alive and functional without AC, which is what civilian preparedness has to assume.
One thing this week: if it is currently spring or early summer, do Action 1 today. Find your cool room. Confirm it is actually cool. The rest follows from that decision.