The Wet Bulb Globe Temperature (WBGT), according to the National Weather Service, is a measure of heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle, and cloud cover (solar radiation). This differs from the heat index, which takes into consideration temperature and humidity and is calculated for shady areas.
| Level | Temperature Range | Description |
|---|---|---|
| Low | < 80°F | Safe for most outdoor activities. |
| Moderate | 80°F – 84°F | Caution: risk for high-intensity activities. Take breaks and hydrate. |
| High | 84°F – 88°F | Increased risk of heat illness. Frequent rest breaks recommended. |
| Very High | 88°F – 90°F | Heat illness likely with prolonged activity. Limit outdoor activities. |
| Extreme | > 90°F | Extreme caution! Heat stroke is possible. Avoid strenuous outdoor activities. |