Parked Car Solar Heat Risk Calculator
Estimate how quickly a vehicle cabin heats up under direct sunlight, using published measurements. A reminder of why children and pets must never be left in a parked car
Current Outside Temperature
Supported range: 60°F (16°C) to 115°F (46°C)
A Lawrence Berkeley National Laboratory study reported a roughly 9–11°F (5–6°C) cabin difference between identical silver and black cars after 1 hour in direct sun. Here the color adjustment is approximate.
Why a Parked Car Heats Up So Fast
Vehicles heat up quickly because sunlight is trapped inside. Visible and near-infrared sunlight passes largely through the window glass and warms interior surfaces such as the dashboard, seats and steering wheel. These surfaces re-emit the energy as longwave infrared heat, which glass does not easily let back out.
Common misconception: Cracking the windows 1–2 inches has been found to make little difference to how fast the cabin heats up, and does not make it safe to leave a child or pet inside.
Estimated Cabin Temperature
How to use this tool
- Enter the outside air temperature and choose °F or °C with the unit switch (supported range: 60–115 °F / 16–46 °C).
- Pick the car's color group: light, medium or dark. Interior color and tint matter too, so choose the closest match.
- Read the estimated cabin temperature after 10, 20, 30 and 60 minutes, then use the copy button to keep the result.
- Treat the numbers as a planning estimate: sun angle, windows left open and sunshades change the real figure.
Worked example
With the defaults (85 °F outside, medium color) the tool estimates a rise of about 19 °F after 10 minutes, so the cabin is near 104 °F (40 °C). After 30 minutes it is near 119 °F (48 °C) and after an hour near 128 °F (53 °C). The takeaway: most of the heating happens in the first half hour, so a quick errand is not a safe window for a child, a pet or a person who cannot open the door themselves.
Why this tool exists and where its numbers come from
A parked car heats up quickly even on mild days, and children and pets have died in them. The temperature rises used here are averages from published measurements, not a prediction for a specific car, and a child or pet should never be left alone in a vehicle.
Sources
- Stanford Medicine (2005): Parked cars get dangerously hot even on cool days
- McLaren, Null & Quinn, Pediatrics 2005: Heat stress from enclosed vehicles (full text, copy)
- NHTSA: Child heatstroke prevention
For the full method, see the Methodology section just below.
Methodology
The temperature rises used here come from published vehicle-heating measurements: McLaren C, Null J, Quinn J. “Heat stress from enclosed vehicles”, Pediatrics 2005;116(1):e109–e112, and the vehicle-heating data compiled by meteorologist Jan Null (NoHeatStroke.org). They are averages, not predictions for a specific vehicle.
Five hot days, one pattern: outside vs. inside
Cabin air for a medium-colored car, exactly as the tool displays it (rounded to whole degrees):
| Outside | After 10 min | After 30 min | After 60 min |
|---|---|---|---|
| 70 °F (21 °C) | 89 °F (32 °C) | 104 °F (40 °C) | 113 °F (45 °C) |
| 80 °F (27 °C) | 99 °F (37 °C) | 114 °F (46 °C) | 123 °F (51 °C) |
| 90 °F (32 °C) | 109 °F (43 °C) | 124 °F (51 °C) | 133 °F (56 °C) |
| 100 °F (38 °C) | 119 °F (48 °C) | 134 °F (57 °C) | 143 °F (62 °C) |
| 110 °F (43 °C) | 129 °F (54 °C) | 144 °F (62 °C) | 153 °F (67 °C) |
How to read it: the tool adds a fixed rise (+19, +34 and +43 °F at 10, 30 and 60 minutes), so a day that is 10 °F warmer shifts every cell by 10 °F. It only calculates from 60 to 115 °F outside; beyond that it shows dashes.
A case: Lena drives a dark hatchback and it is 35 °C (95 °F) outside. She thinks of a 30-minute stop. With the dark setting (rise x 1.116) the tool shows 116 °F (47 °C) after 10 minutes and 133 °F (56 °C) after 30. The same day in a light car (x 0.884) gives 125 °F (52 °C) after 30. Color changes the figure by a few degrees, but neither car is anywhere near comfortable.
These are averages for the air only; seats and dashboards run hotter, and there is no safe time to leave a child or pet alone in a parked car.
Ways to Keep a Parked Car Cooler
Accessories that reflect sunlight and can reduce heat build-up for comfort. They never make it safe to leave a child or pet in a parked car.
Foldable Car Windshield Sunshade Umbrella (UV Reflector)
A foldable windshield sunshade that opens like an umbrella, according to the listing. It blocks direct sun on the glass while the car is parked.
Magnetic Exterior Windshield Sun & Heat Cover
An exterior windshield cover held by magnets, according to the listing. It shades the glass from outside, before the sun reaches the cabin.
Solar Powered Car Window Ventilation Cooler
A solar-powered fan that fits in a slightly open window, according to the listing, to move air while the car is parked. It does not replace the safety rules in the calculator: never leave a child or pet in a parked car.
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Frequently asked questions
Does cracking the windows prevent heat accumulation? ▼
No. Measurements (McLaren et al., Pediatrics, 2005) found that cracking the windows 1 to 2 inches made little difference to how much the cabin heated up. It is not a safe way to leave a child or pet in a parked car.
Can a car get dangerously hot on a cool, cloudy day? ▼
Yes. Fatalities have occurred on days with ambient temperatures as low as 70°F (21°C). Even through broken clouds, infrared and UV radiation readily heat darker dashboards and vehicle interiors.
How much does the vehicle's color affect interior temperature? ▼
Darker colors absorb more sunlight. A Lawrence Berkeley National Laboratory study reported a cabin temperature difference of roughly 9–11°F (5–6°C) between identical silver and black cars after an hour in direct sun. This tool applies only a rough color adjustment.
What does the tool show for a typical warm day, and why does it show dashes outside some temperatures? ▼
At 80°F (27°C) outside with a medium-colored car, the tool shows about 99°F after 10 minutes, 109°F after 20, 114°F after 30 and 123°F after 60. A light exterior scales the rise by 0.884 and a dark one by 1.116, so a dark car at 80°F reaches about 128°F after an hour. The fixed rises are averages from measurements at moderate to hot weather, so the tool only calculates between 60°F and 115°F (about 16°C to 46°C) outside and shows dashes beyond that instead of extrapolating.
Does this tell me how long a child or pet can safely stay in the car? ▼
No. The tool estimates the air temperature in a parked car only. It cannot say how long a child or animal can tolerate it, and seats, dashboards and steering wheels can be considerably hotter than the air. There is no safe duration for leaving a child or pet alone in a parked vehicle, even briefly. If you see a child or animal alone in a hot car, call your local emergency number right away.