Heat safety
Parked Vehicle Heat Risk Estimator
Vehicles can reach lethal temperatures within minutes, even on mild days. This calculator models interior heat rise using published research from pediatric heatstroke prevention studies. Always use with caution and never leave children or pets unattended.
Ambient
86.0 °F / 30.0 °C
Interior temperature
138.5 °F
59.2 °C
Life-threatening heatstroke can occur within minutes. Never leave people or pets unattended.
How to Use This Calculator
Measure ambient conditions
Use the forecast or thermometer reading for your location.
Select vehicle characteristics
Choose color intensity and whether windows are closed or cracked.
Review risk and act
Use the projected interior temperature to communicate danger and reinforce immediate removal of occupants.
Formula
Interior temperature rise = Max rise × (1 − e−k·t)
Max rise adjusted for vehicle color; rate constant k depends on ventilation (closed vs. cracked windows).
Interior temperature = Ambient + Temperature rise.
Model calibrated to peer-reviewed pediatric vehicular heatstroke studies (McLaren et al., Pediatrics 2005; Grundstein et al., 2010).
Full Description
Interior vehicle temperatures can rise rapidly because of the greenhouse effect: solar radiation penetrates windows, heating interior surfaces, while limited airflow traps heat. Even on 70°F (21°C) days, cars can exceed 115°F (46°C) within 30 minutes. Children are especially vulnerable due to reduced thermoregulation.
This calculator estimates temperatures for educational and advocacy purposes. Actual conditions vary with sun angle, humidity, wind, vehicle type, and color. Always act on the precautionary principle—no amount of time is safe for unattended occupants.
Frequently Asked Questions
Do cracked windows make a difference?
Only marginally. Studies show minimal temperature reduction with windows cracked. Never rely on this for safety.
What about cloudy days?
Vehicles can still heat rapidly because UV and infrared radiation penetrate cloud cover. Always assume risk.
How fast can interior temps rise?
Life-threatening temperatures can occur within 10–15 minutes. Heatstroke can develop quickly in children and pets.
What preventive steps can I take?
Use reminders (phone alerts, stuffed animal in front seat), lock unattended cars, and call emergency services if a child or pet is trapped.