The thermometer measures the air. Your body is also dealing with the humidity, the wind and the sun. Two places can both read 90°F and be very different places to work, train, or walk a dog.

WetBulbTracker computes wet-bulb globe temperature - WBGT, the measure that militaries, athletic associations and occupational-safety standards actually use - for any point on Earth. It accounts for humidity, wind, cloud cover and direct sun, which is why it so often disagrees with the number on your weather app, and why the disagreement matters.

WHAT YOU GET, FREE, WITHOUT AN ACCOUNT

• Live heat stress anywhere on Earth, sun and shade
• Plain-language guidance: what to change, not just a number
• A live map you can scrub through the next 24 hours
• Pavement and paw safety, including how long asphalt stays dangerous after sunset
• "Safe for me": an optional personal read for age, exertion, heat adaptation and health sensitivities
• State high-school athletic policy tables, cited to their source
• City guides for 176 US metros
• Today's report, and viewing any report someone shares with you

The readings, the guidance and the personal read are free forever, not a trial. Viewing a shared report never asks you to sign in.

WITH A FREE ACCOUNT

• Heat alerts before conditions cross a level you choose
• Three saved places

HOW ACCURATE IS IT?

We publish that, continuously, at wetbulbtracker.com/validation: our WBGT against the U.S. National Weather Service's own published WBGT, refreshed as new forecasts arrive. Both are modeled rather than measured, and we say so on the page. A conditions-based correction reduced our error by about 31% on cities the model had never seen.

We would rather show you the error bars than claim we do not have any.

FOR WORK, SPORT AND SERVICE

Purpose-built views for outdoor work, athletics and tactical use, each carrying the guidance that field actually uses, attributed to whoever wrote it.

PAID PLANS (OPTIONAL)

Plus adds the week ahead, any hour of the map two days out, reports for any date range back five years, deeper alerts, unlimited saved places, CSV export, and reports emailed to you on a schedule.

Pro adds Studio: multi-site documents with your organization's name and logo, a dated record of what the conditions were and how they were computed, the kind of artifact an organization's own record-keeping can cite.

WHAT THIS IS NOT

Our numbers are modeled from gridded weather data, not measured at your location by an instrument. Where a standard, contract or policy requires an on-site measured reading, that instrument is the one that governs. Use this to plan the day, pick the window, and know what to expect before you get there.

This app is informational. It is not a medical device and does not diagnose, treat, cure, or prevent any medical condition. Consult a healthcare professional for medical advice, diagnosis, or treatment. This app is not a substitute for official heat warnings from your weather service - always follow your local authorities.

WBGT is computed by the Liljegren (2008) method from Open-Meteo data.