How HeatGuard turns weather into planning context.

HeatGuard requests a three-day forecast from WeatherAPI using the selected location's latitude and longitude. Forecast responses are cached server-side for six hours to limit repeated upstream requests. The displayed update time is the provider forecast hour used for the current conditions.

Weather forecasts are estimates and can change. A provider observation may also represent conditions away from the exact street, field, trail or jobsite.

Heat index is calculated in Fahrenheit from air temperature and relative humidity. In hot conditions, HeatGuard uses the National Weather Service Rothfusz regression with the standard low-humidity and high-humidity adjustments. At cooler inputs, it uses the NWS simple approximation.

The standard heat index describes shaded, light-wind conditions. Direct sun and hot surfaces can add exposure beyond the displayed value.

HeatGuard's WBGT is modeled—not measured. It first estimates natural wet-bulb temperature from air temperature and relative humidity using the Stull approximation. It then combines 70% estimated wet bulb with 30% air temperature and adds a 1.8°C daytime solar allowance.

This simplified model does not use a physical black-globe reading and cannot resolve local shade, surface radiation, clothing or a field-level microclimate. Never use it instead of a required on-site instrument or compliance procedure.

HeatGuard scores consecutive forecast hours using heat-risk category, temperature and UV. It recommends the three-hour window with the lowest combined score in the available daylight preview. This is a comparison between forecast hours—not a declaration that the window is safe for every person or activity.

Heat response varies with exertion, duration, clothing, acclimatization, medication, age and health. HeatGuard does not know those personal factors and does not diagnose illness. Conditions can also differ sharply over short distances.

Use official alerts, applicable organizational protocols and on-site judgment. Call emergency services for suspected heat stroke, confusion, collapse or another emergency.