About HeatSafe

What is HeatSafe?

HeatSafe shows the Heat Safety Index for any location — a single number that tells you whether your body can cool itself in current outdoor conditions.

Most weather services report outdoor temperature. Outdoor temperature alone does not tell you whether the heat is safe for your body. A dry 42°C in Jaipur may be more survivable than a humid 34°C in Chennai, because your body cools itself through sweat evaporation — and high humidity stops evaporation.

The Heat Safety Index combines outdoor temperature and humidity into one number that answers the question weather forecasts don't: can your body handle today's heat?

What HeatSafe is not

HeatSafe is informational, not diagnostic. Three boundaries are worth stating explicitly:

• Not a medical device. The Heat Safety Index doesn't account for individual health conditions, age, medications, fitness, or hydration. If you or someone around you shows symptoms of heat illness, see the Disclaimer for emergency guidance.
• Not a personal risk assessment. The reading describes the conditions, not your body's response to them. Vulnerable groups — elderly, infants, pregnant women, people with chronic illness — face higher risk at every reading.
• Not a replacement for official alerts. When IMD or local authorities issue heatwave warnings, follow them. HeatSafe is one input alongside official guidance — useful between alerts, not above them.

Calibration, not alarm

HeatSafe is built to calibrate, not alarm. Heat doesn't always look dangerous, and dangerous heat doesn't always look extreme. Most weather reports give you the temperature; HeatSafe tells you what your body can handle.

The point is not to scare people but to help them decide — about hydration, shade, timing, and breaks — using the things they actually control. The temperature, humidity, and the day itself are not in your hands. What you do with them is.

The science in one sentence

When the Heat Safety Index exceeds 32°C, even a healthy adult at rest in the shade cannot cool their body through sweating. This is a physiological limit, not a matter of fitness or willpower.

Why HeatSafe exists

India experiences some of the most dangerous heat conditions on earth. Heat-related deaths are undercounted, underreported, and preventable. Public awareness of wet bulb temperature — the scientific measure behind the Heat Safety Index — is almost zero.

HeatSafe fills an information gap. Whether it saves many lives, some, or proves informative but not behaviour-changing will be measured over time. The conviction behind it: even one life saved makes it worth building.

Who built it

HeatSafe is a one person project from Coimbatore, Tamil Nadu, built in the summer of April 2026 — using AI as a technical collaborator. It is free, ad-free, and will remain so.

Privacy

HeatSafe collects no personal data, stores nothing, and shares nothing. See the Privacy page for details.

Data sources

• Weather data: Open-Meteo (open-source, free)
• Wet bulb formula: Stull (2011)
• Physiological thresholds: Vecellio et al. (2022)
• Geocoding: Open-Meteo Geocoding API, Nominatim

Contact

hello@heatsafe.in