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Heat Index Procedures

Heat Index Procedures for Outdoor Activities When determining outside activities (athletic practice, physical education, recess, etc.), Walla Walla Public Schools relies on the WIAA Heat Index recommendations to inform their safety and mitigation measures.  

Background:

  • A heat index is an index that combines air temperature and relative humidity in an attempt to determine the human-perceived equivalent temperature; "how hot it feels." The result is also known as the "felt air temperature" or "apparent temperature." For example, when the temperature is 90°F with very high humidity, the heat index can be about 106°F.
  • The human body normally cools itself by perspiration, or sweating. Heat is removed from the body by evaporation of that sweat. However, relative humidity reduces the evaporation rate because the higher vapor content of the surrounding air does not allow the maximum amount of evaporation from the body to occur.
  • Higher humidity results in a lower rate of heat removal from the body, hence the sensation of being overheated.  
  • The table below is a listing of the calculated heat index values which match the U.S. National Oceanic and Atmospheric Administration's table. The colors correspond to WIAA’s and WWPS’ categorization (notice, caution, warning, and danger).
  • Looking at the table, it is important to note that any temperature above 86°F will "feel" at least 86°F. Virtually every heat index will be at least the current temperature, if not hotter. 
Temperature Table

Procedures:

  • The WIAA & WWPS use a custom script to calculate a given heat index and forecasted heat index for a given location (i.e. city name or ZIP code). This is accomplished via a weather API service through AccuWeather.  

HEAT INDEX ≥ 105°F: DANGER

  • Stop all outside activity in practice and/or play.  
  • Indoor activity may need to be altered if air conditioning is not available. 

HEAT INDEX ≥ 100°F AND < 105°F: WARNING

School Activities:

  • If practical, move outside activities indoor.
  • Limit intensity and/or duration of outside activities (e.g. walking instead of running, low impact activities, breaks between exertions).  
  • Provide access to water.
  • Watch/monitor students for necessary action.

WIAA Athletic Activities:

  • Maximum of 4 hours of practice per day.
  • Practice length a maximum of 2 hours, one practice shall be during a time of day with a lower heat index.
  • Mandatory 3-hour recovery period between practices.
  • Water shall always be available and athletes should be able to take in as much water as they desire.
  • Watch/monitor athletes for necessary action.
  • See WIAA website for more details: https://www.wiaa.com/health-wellness

HEAT INDEX ≥ 95°F AND < 100°F: CAUTION

School Activities:

  • Consider limiting intensity and/or duration of outside activities (e.g. walking instead of running, low impact activities, breaks between exertions).  
  • Provide access to water.
  • Watch/monitor students for necessary action.

WIAA Athletic Activities:

  • Maximum of 4 hours of practice per day.
  • Practice length a maximum of 2 hours.
  • Mandatory 3-hour recovery period between practices.
  • Water shall always be available and athletes should be able to take in as much water as they desire.
  • Watch/monitor athletes for necessary action.
  • See WIAA website for more details: https://www.wiaa.com/health-wellness

HEAT INDEX ≥ 80°F AND < 95°F: NOTICE

School Activities:

  • Watch/monitor students for necessary action.

WIAA Athletic Activities:

  • Maximum of 5 hours of practice per day in divided sessions.
  • Water should always be available and athletes should be able to take in as much water as they desire.
  • Watch/monitor athletes for necessary action. 

HEAT INDEX < 80°F: SAFE FOR MOST PARTICIPANTS

School Activities:

  • Watch/monitor students for necessary action.

WIAA Athletic Activities:

  • Maximum of 5 hours of practice per day in divided sessions.
  • Water shall always be available and athletes should be able to take in as much water as they desire.
  • Watch/monitor athletes for necessary action. 
thermometer