How fast does a parked car heat up?
Set today's temperature and where you parked. Then watch an hour pass in a few seconds, and see what happens to everything you left inside.
What happens, and when
Two hours parked: sun or shade
About 80% of the rise happens in the first 30 minutes. Shade helps a lot. Cracking a window barely helps at all.
What to do
Not even for a minute, not even with the windows open. If you see a child alone in a car, call 999.
Phones, laptops and power banks come with you. Never charge them in a hot car. If one swells, smells or is hot, let it cool away from the car.
Insulin and many medicines must stay below about 25–30°C. Check the leaflet.
Do the supermarket at the end of your trip. Keep lighters, aerosols and perfume out of the car in summer.
Estimate based on studies that measured car cabins (McLaren et al., 2005; Vanos et al., 2018): 20–25°C above outside air after an hour in full sun. Not medical or safety advice. Live outside temperature from Open-Meteo.