Guide

How fast a parked car heats up: the minute-by-minute temperature curve

How fast does the temperature rise inside a parked car?

Peer-reviewed vehicle heating studies (McLaren et al., Pediatrics) show that on sunny days, a parked car's interior temperature rises by an average of 3.2°F every 5 minutes during the first half hour. Roughly 80% of the total temperature rise happens in the first 30 minutes: +19°F (10.6°C) after 10 minutes, +29°F (16.1°C) after 20 minutes, +34°F (18.9°C) after 30 minutes, and +43°F (23.9°C) after 60 minutes—even when windows are cracked 1.5 inches.

How many degrees does a parked car heat up in 10, 20, 30, and 60 minutes?

In direct sun, a parked car's cabin temperature jumps an average of +19°F (+10.6°C) in 10 minutes, +29°F (+16.1°C) in 20 minutes, +34°F (+18.9°C) in 30 minutes, and +43°F (+23.9°C) in 60 minutes above outside air temperature. Shortwave sunlight passes easily through automotive windshields and side glass, heating the dashboard, steering wheel, and seats (which often exceed 160°F to 190°F surface temperature). Those heated interior surfaces emit longwave infrared radiation that cannot pass back out through the glass, while the sealed cabin blocks convective wind cooling.

Average cabin temperature rise above outside air temperature on sunny days (McLaren et al.).
Elapsed Time Parked	Cabin Temp Increase	Cabin at 75°F Outside	Cabin at 90°F Outside
0 minutes (AC off)	+0°F (0°C)	75°F (23.9°C)	90°F (32.2°C)
10 minutes	+19°F (+10.6°C)	94°F (34.4°C)	109°F (42.8°C)
20 minutes	+29°F (+16.1°C)	104°F (40.0°C)	119°F (48.3°C)
30 minutes	+34°F (+18.9°C)	109°F (42.8°C)	124°F (51.1°C)
60 minutes	+43°F (+23.9°C)	118°F (47.8°C)	133°F (56.1°C)

Does cracking car windows keep a parked car from overheating?

No—cracking all four car windows by 1.5 inches (4 cm) slows cabin heating from 3.4°F to 3.1°F per 5 minutes, lowering the 30-minute interior temperature by only 2°F to 3°F (1.1°C to 1.7°C). In controlled experiments comparing closed windows against windows cracked 1.5 inches (4 cm) on all four doors, the heating rate dropped from 3.4°F per 5 minutes to 3.1°F per 5 minutes—reducing the 30-minute cabin temperature by only about 2°F to 3°F. A narrow window gap does not create enough cross-ventilation to overcome 600 to 900 W/m² of solar radiation pouring through the windshield.

Can a parked car reach dangerous temperatures on a mild 72°F (22°C) day?

Yes—even on a pleasant 72°F (22°C) sunny afternoon, trapped solar radiation heats a parked car cabin past 106°F (41°C) in 30 minutes and 115°F (46°C) within 60 minutes. Because cabin heating is driven primarily by direct shortwave solar irradiance rather than ambient air temperature, a clear 72°F (22°C) spring afternoon heats a parked vehicle past 106°F in 30 minutes and 115°F in an hour—crossing dangerous thresholds for infants, young children, and pets even when outdoor weather feels pleasant.

Common questions

Does pre-cooling the car with air conditioning give you a safe buffer after parking?

No. Instrumented vehicle studies found that pre-cooling the cabin with AC only delays reaching dangerous temperatures by about 5 minutes once the engine is turned off in the sun.

Do white or silver cars stay safe inside when parked in the sun?

No. While a white exterior roof stays slightly cooler than a black roof, most solar heat enters directly through the glass windows and heats the dark dashboard and upholstery—so cabin air temperatures differ by only a few degrees.

Why are infants and dogs at much higher risk in a hot car than adults?

Infants have a higher surface-area-to-mass ratio and immature thermoregulation, heating 3 to 5 times faster than adults; dogs rely on panting rather than full-body sweating, which fails rapidly once cabin air approaches body temperature.

Does a windshield sunshade stop a parked car from getting dangerously hot?

A reflective windshield sunshade lowers dashboard surface temperatures so the steering wheel isn't scalding to touch, but side and rear windows still admit enough solar energy to push cabin air to dangerous levels within 20 to 30 minutes.