Measuring Heat
Wimbledon uses the Heat Stress Index (HSI), which is similar to the U.S. Heat Index, but also includes the surface temperature of the court to determine the use of the Women’s Tennis Association’s (WTA) Heat Policy.
The Heat Rule was introduced in 1992 and is used at all WTA events throughout the year. The rule allows a 10-minute break to be taken between the second and third set when the HSI is at or above 30.1°C (86°F). Readings of the heat stress are taken 30 minutes prior to the start of play and then at 2:00 pm and 5:00 pm. The Heat Rule only applies to ladies’ matches and can be implemented if one of the players requests a break for the heat.
Currently, there is no similar rule for the men on the Association of Tennis Professionals (ATP) World Tour.
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