| Webster's Online Dictionary |
| Expressions | Domain | Definition | |
| Heat index | Aerospace | The difference between the absolute visual magnitude of a star and the absolute radiometric magnitude (Mv - Mr). (references) | |
| Heat index | Weather | 1: The apparent temperature that describes the combined effect of high temperatures and high levels of humidity. (references) | |
| 2: The apparent temperature of exposed skin when exposed to air with a high moisture content. Dry air allows evaporative cooling of the skin's surface. The higher the humidity, the less the skin can cool itself with evaporative cooling. (references) | |||
| 3: The Heat Index (HI) or the "Apparent Temperature" is an accurate measure of how hot it really feels when the Relative Humidity (RH) is added to the actual air temperature. To find the Heat Index (HI), look at the Heat Index (HI) Chart below. As an example, if the air temperature is 90 F (found at the left side of the table) and the Relative Humidity (RH) is 70% (found at the top of the table), the Heat Index (HI)--or how hot it actually feels--is 106 F. This is at the intersection of the row 90 F and the 70% column. This index was devised for shady, light wind conditions. Exposure to full sunshine can increase Heat Index (HI) values by up to 15 F. Also strong winds, particularly with very hot, dry air, can be extremely dangerous. Any value Heat Index (HI) greater than 105 F is in the Danger Category. This is denoted by a thick line on the chart. Any number below or to the right of the thick line is in this category. When the Heat Index is between 105-115 F for 3 hours or more, a Heat Advisory will be issued by the local National Weather Service Forecast Office (NWSO). If the Heat Index is greater than 115 F for 3 hours or more, an Excessive Heat Warning will be issued by the local National Weather Service Forecast Office (NWSO). See Apparent Temperature. (references) | |||
| 4: An index that combines air temperature and humidity to give an apparent temperature (how hot it feels). (references) | |||
| Heat Index (HI) | Aerospace | A value that represents the temperature it actually feels at a given air temperature and relative humidity. (references) | |
Source: compiled by the editor from various references; see credits. | Top | ||
