Humidity
When temperatures combine with high humidity, it may feel hotter outside than it actually is. This is known as the Heat Index (HI). High heat index values limit the body’s ability to cool off through sweating. As sweat evaporates from the skin, it cools the body temperature. When the heat index is over 105°F, conditions can become dangerous to people and animals.
Another way to measure the effects of high humidity is Wet Bulb Globe Temperature (WBGT). WBGT is not measure the same as HI, as it also takes into account the angle of the sun, wind speed and cloud cover.
With higher values of HI and WBGT, people become more susceptible to:
- sunstroke
- heat cramps
- heat exhaustion
- heat stroke
Source: Heat Index| National Weather Service
| Category | WBGT°F | WBGT°C | Flag Color |
|---|---|---|---|
| 1 | <= 79.9 | <= 26.6 | White |
| 2 | 80 - 84.9 | 26.7 - 29.3 | Green |
| 3 | 85 - 87.9 | 29.4 - 31.0 | Yellow |
| 4 | 88 - 89.9 | 31.1 - 32.1 | Red |
| 5 | => 90 | => 32.2 | Black |