Road Runners Club of America

Growing the Sport of Running Since 1958

Event Alert System

The Event Alert System, or EAS, is a color-coded method of quickly communicating to participants the potential for adverse weather conditions that can affect the race event. A series of color codes is used to indicate the increasing severity of adverse conditions as outlined below:
Download the PDF version for use in print materials

These adverse conditions are most usually related to heat stress. However, the system could also be used to warn of other potentially dangerous situations, such as cold, storms, tornadoes, or even non-weather situations like auto accidents or fires on or near the course.

This system, and the scientific measurements behind it, was originally developed by the United States military, as a guide to the level of heat stress soldiers might experience during training exercises in varying weather conditions. The system was adopted by the American College of Sport Medicine and now the RRCA is encouraging all events to implement a similar system.  This system has been used by events such as the Bank of America Chicago Marathon,the IMT Des Moines Marathon and the Medtronic Twin Cites Marathon.

Heat Stress Calculation

The heat stress is calculated using a special scientific instrument, designed for that purpose. There are versions that can be permanently mounted in a fixed position, such as the side of building, and there are portable, handheld versions. The proper term for what is being measured is the Wet Bulb Globe Temperature Index, or WBGT Index. This index is expressed in either degrees of Celsius or degrees of Fahrenheit, depending on how you want your device to report.  The WBGT Index is calculated using an accepted mathematical formula that takes into account the following variables:

  • Ambient temperature (the usual “weatherman forecast” temperature)
  • Relative humidity
  • Solar radiation (not the “glow in the dark” kind, but rather the “sunshine on a black car hood” kind)
  • The cooling effect of wind

The color codes correspond to specific parameters of the WBGT Index, with each color changing as the severity of the WBGT Index rises.

  • Green – low risk – a WBGT Index of less than or up to 84.9F (29.3C)
  • Yellow – moderate risk – a WBGT Index of between 85F to 87.9F (29.4C and 31C)
  • Red – high risk – a WBGT Index of between 88F to 89.9F (31.1C and 32.1C)
  • Black – extreme risk – a WBGT Index of more than 90F+ (32.2C)

Buy a Wet Bulb Thermometer for your Event

Be sure to include information in your race packet and your event emails about the Event Alert System.  Display signs or flags at your packet pick-up that coordinate with the current conditions so people are aware of what to look for on course.

On race day, place the EAS near your start line to indicates the current Event Alert code. Take readings several times during the course of the event hour and change the color codes on signs or flags as the WBGT Index readings change. Place EAS signs or flags at several locations along the course. These signs should be placed close to aid stations, as most participants tend to slow down near aid stations and instructions can be given if the EAS code is red or black.  Ensure you have a system in place and a volunteer ready to update the EAS codes as weather conditions on the course change.

If the course needs to be closed to due to “black” conditions, follow these guidelines:

  • Have a course closure plan in place well before your race day.
  • Have the announcer at the start/finish line announce that the race has been shut down due to dangerous heat/weather conditions.
  • All Event Alert System signs on the course will be changed to the black color code.
  • On-course personnel, course marshals, and aid stations will be informed of the course shut down so that they can then communicate the information to participants on course.
  • Require ALL AID STATIONS TO REMAIN OPEN until the course has been cleared of participants and the aid station receives official instructions to close down.
  • Follow-up with participants following the event to remind them that safety is paramount and apologize for making the tough call to cancel the event due to dangerous weather conditions.

Adapted from information found on the Queen City Marathon website

Join RRCA Today

Dedicated to providing quality resources for running clubs, events, and coaches.

Donate to the RRCA

A 501(c)3 organization ​dedicated to growing running for all ages and abilities.

Subscribe to Email Updates

Keep Pace with monthly emails from RRCA.

Road Runners Club of America