STANDARDS SECTION XVIII - TOURNAMENT STANDARDS OF PERFORMANCE Index (Wet-Bulb Globe Temperature (WBGT)) meets or exceeds the  levels stated below for Extreme Weather Conditions - Modification of  Play and Extreme Weather Conditions - Suspension of Play. If a WBGT  meter is not available for measuring the Heat Stress Index (WBGT),  then the Heat Index (Apparent Temperature) should be calculated  based on the chart below. Air Temperature (Celsius/Fahrenheit) 21.1°C 70°F 23.9°C 75°F 26.7°C 80°F 29.4°C 85°F 32.2°C 90°F 35.0°C 95°F 37.8°C 100°F 40.6°C 105°F 43.3°C 110°F 46.1°C 115°F 48.9°C 120°F Relative  Humidity Heat Index (Apparent Temperature) (combined index of air temperature and relative humidity) 0% 17.8°C 64°F 20.6°C 69°F 22.8°C 73°F 25.6°C 78°F 28.3°C 83°F 30.6°C 87°F 32.8°C 91°F 35.0°C 95°F 37.2°C 99°F 39.4°C 103°F 41.7°C 107°F 10% 18.3°C 65°F 21.1°C 70°F 23.9°C 75°F 26.7°C 80°F 29.4°C 85°F 32.2°C 90°F 35.0°C 95°F 37.8°C 100°F 40.6°C 105°F 43.9°C 111°F 46.7°C 116°F 20% 18.9°C 66°F 22.2°C 72°F 25.0°C 77°F 27.8°C 82°F 30.6°C 87°F 33.9°C 93°F 37.2°C 99°F 40.6°C 105°F 44.4°C 112°F 48.9°C 120°F 54.4°C 130°F 30% 19.4°C 67°F 22.8°C 73°F 25.6°C 78°F 28.9°C 84°F 32.2°C 90°F 35.6°C 96°F 40.1°C 104.2°F 45.0°C 113°F 50.6°C 123°F 57.2°C 135°F 64.4°C 148°F 40% 20.0°C 68°F 23.3°C 74°F 26.1°C 79°F 30.0°C 86°F 33.9°C 93°F 38.3°C 101°F 43.3°C 110°F 50.6°C 123°F 58.3°C 137°F 66.1°C 151°F 50% 20.6°C 69°F 23.9°C 75°F 27.2°C 81°F 31.1°C 88°F 35.6°C 96°F 41.7°C 107°F 48.9°C 120°F 57.2°C 135°F 65.6°C 150°F 60% 21.1°C 70°F 24.4°C 76°F 27.8°C 82°F 32.2°C 90°F 37.8°C 100°F 45.6°C 114°F 55.6°C 132°F 65°C 149°F 70% 21.1°C 70°F 25.0°C 77°F 29.4°C 85°F 33.9°C 93°F 41.1°C 106°F 51.1°C 124°F 62.2°C 144°F 80% 21.7°C 71°F 25.6°C 78°F 30.0°C 86°F 36.1°C 97°F 45.0°C 113°F 57.8°C 136°F 90% 21.7°C 71°F 26.1°C 79°F 31.1°C 88°F 38.9°C 102°F 50.0°C 122°F Extreme Heat Condition – Modification of Play Extreme Heat Condition – Suspension of Play ii.  Modification of Play iii.  Suspension of Play Extreme Weather Condition - Modification of Play shall be defined as  when the Heat Stress Index (WBGT) meets or exceeds 30.1 degrees  Celsius/86.2 degrees Fahrenheit or when the Heat Index (Apparent  Temperature) meets or exceeds 34.0 degrees Celsius/93.2 degrees  Fahrenheit. Extreme Weather Condition - Suspension of Play shall be defined as  when the Heat Stress Index (WBGT) meets or exceeds 32.2 degrees  Celsius/90.0 degrees Fahrenheit or when the Heat Index (Apparent  Temperature) meets or exceeds 40.1 degrees Celsius/104.2 degrees  Fahrenheit. 364