Never leave them in the car. Free, no login, runs in your browser.

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Since 1998, 1,047 US children have died of vehicular hyperthermia (NoHeatstroke.org, Jan Null SJSU). All of those deaths were preventable. McLaren, Null & Quinn (2005, Pediatrics) established that a parked car rises ~22°C above ambient within 60 min, and that the cabin reaches dangerous temperatures even on mild 22°C spring days.

HotCarWatch takes the outdoor temperature, sun exposure, vehicle type, and the planned away time, and tells you:

• The cabin air temperature at your planned return
• The occupant core body temperature (child, toddler, infant, small/medium/brachycephalic dog, cat)
• The time to heat-stroke milestones (40°C, 42°C)
• A ranked list of interventions, with the only guaranteed-safe option clearly marked

Running the frontend

cd frontend
python3 -m http.server 8000
# open http://127.0.0.1:8000/

The four files (index.html + app.js + styles.css + about.html) total 27 KB raw, 8.8 KB gzipped. Drop them on any static host (GitHub Pages, S3, Cloudflare Pages, Netlify) and they work. $0 operating cost.

Running the Python library

pip install -e .

from hotcarwatch import (
    VEHICLE_ARCHETYPES, OCCUPANT_ARCHETYPES,
    simulate_cabin, hyperthermia_timeline,
)

veh = VEHICLE_ARCHETYPES["midsize_sedan_dark"]
sim = simulate_cabin(veh, T_outdoor_C=27.0, solar_W_per_m2=900.0, hours=2.0)
occ = OCCUPANT_ARCHETYPES["toddler_2y"]
risk = hyperthermia_timeline(occ, sim)
print(f"Cabin peak: {sim.peak_T_C:.1f} C")
print(f"Toddler core 40 C at t = {risk.time_to_40C_h*60:.0f} min")

Running experiments

make experiments    # validation, scenarios, interventions
make figures        # paper/figures/*.pdf
make paper          # paper/hotcarwatch.pdf
make test           # 15 unit tests

Project layout

hotcarwatch/     Python library: cabin thermal model, occupant hyperthermia,
                 vehicle archetypes, scenarios, interventions
frontend/        static web app (no build step, no dependencies)
experiments/     validation, scenario, and intervention scripts
results/         JSON outputs of the experiments
paper/           LaTeX source and compiled PDF
tests/           unit tests

Validation

All 16 published cases (McLaren 2005 cabin-rise data at 22°C and 32°C ambient; Vanos 2018 sun-vs-shade delta; NIA/ASHRAE thermal time constants for 7 vehicle archetypes) reproduce within tolerance. See results/validation.json and the paper's §3.

Privacy

HotCarWatch does not phone home. No network calls, no analytics, no cookies. Vehicle profile is stored in browser localStorage only.

The Most Important Thing

The only intervention that prevents heat injury with certainty is: do not leave any child or animal in any parked vehicle for any length of time.

Cracking the windows does not help. Cloudy days are still dangerous. "Just for a minute" is a primary documented cause of death.

License

Public domain (CC0 1.0). See LICENSE.