Tennis players and fans are facing more extreme weather at the four Grand Slams

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Sporting events around the world are being impacted by extreme weather, including heat and heavy rainfall, and tennis is no exception. A number of tennis tournaments have been impacted by extreme heat in recent years, with both players and spectators being affected.

Climate Central analyzed temperature and rainfall data at the four Grand Slam tennis tournaments — the Australian Open, French Open, Wimbledon and the U.S. Open — from 1970-2025 to understand how extreme weather has changed over time, and how climate change has played a role. 

Hot days are increasing across all four Grand Slams

The analysis found that the likelihood of a hot tournament day has increased for all four tournaments since 1970. A hot tournament day is defined as having a temperature of 28°C (82°F) or higher — these conditions are noticeably hot for all four Grand Slam host cities, and are a consistent indicator of player heat stress when combined with humidity and sun exposure. It’s also consistent with the International Tennis Federation’s threshold for cooling breaks (at a wet-bulb globe temperature threshold of 30°C). 

At the U.S. Open, the chance of a hot tournament day rose from 49% in the 1970s to 67% in the 2020s. At Wimbledon, the chance increased from 5% to 9% during the same period.

The French Open has warmed the fastest of the four Grand Slams, with average tournament temperatures increasing by 3.5°C (6.4°F) since 1970, which is the equivalent to 0.64°C per decade. Wimbledon has also warmed substantially, with average tournament temperatures increasing by 2.5°C (4.4°F) since 1970.

The number of hot days during all four of the Grand Slam tournaments has increased since the 1970s. Over the past 55 years, climate change has added 160 extra hot days to the four Grand Slam tournaments in total, including 98 hot days during the U.S. Open. See table below. 

Most of the hot days at the French Open and Wimbledon since 1970 would not have occurred without climate change. Climate change was responsible for 67% of all hot days at the French Open and 61% of all hot days at Wimbledon between 1970 and 2025.

The heat can have a big impact on players as well as fans, and this is why certain procedures have been put in place at some of the tournaments. During Wimbledon, the heat rule allows for a 10-minute break (15 minutes for wheelchair events) to be taken during all single events when the wet-bulb globe temperature is at or above 30.1°C. Factoring in the air temperature, humidity, and the surface temperature, it’s measured 30 minutes prior to the start of play and then at 2 pm and 5 pm.

Heavy rain days are increasing for the French Open and Wimbledon

Beyond hot weather, heavy rain also affects the four Grand Slam tournaments, especially those with outside courts without roofs. This analysis found that the number of heavy rain tournament days — days in the tournament window where precipitation reached or exceeded 10mm — for the French Open, Australian Open, and Wimbledon have increased since 1970.

Extreme weather is already impacting tennis tournaments around the world, and the players and fans will continue to be affected if we continue to warm our planet through human-caused carbon pollution.

METHODOLOGY

Climate Central analyzed daily maximum temperatures and daily precipitation for the host cities of the four Grand Slam tennis tournaments: the Australian Open (Melbourne), French Open (Paris), Wimbledon (London), and the U.S. Open (New York).

Tournament Windows and Analysis Period

For each tournament, we analysed conditions during a fixed tournament window: January 15-February 1 for the Australian Open, May 20-June 10 for the French Open, June 25-July 17 for Wimbledon, and August 20-September 15 for the U.S. Open. The analysis covers the period 1970-2025. Because the exact start and end dates of Grand Slam tournaments vary slightly from year to year, we used fixed windows that encompass the typical dates on which each tournament is held. These windows were selected to capture the full range of possible tournament dates across the historical record while maintaining a consistent comparison period from year to year. Using fixed windows ensures that changes in tournament scheduling do not influence long-term trend estimates for either temperature or precipitation.

Temperature Analysis

Daily maximum temperatures were analyzed using Climate Central's Climate Shift Index (CSI) system. The CSI dataset includes both observed temperatures and counterfactual temperatures, or the temperatures that would have occurred in a world without human-caused climate change. For each tournament city, daily maximum temperatures were extracted from the nearest available climate data grid cell. To estimate the influence of climate change on tournament temperatures, we compared observed daily maximum temperatures with counterfactual daily maximum temperatures for the same dates and locations. The difference between observed and counterfactual temperatures represents the warming attributable to climate change. 

The 28°C (82°F) threshold was selected because it approximates the average 90th-percentile tournament-window temperature across the four Grand Slam host cities, providing a consistent benchmark for unusually hot tournament conditions. Although the International Tennis Federation's Extreme Weather Policy is based on Wet Bulb Globe Temperature (WBGT) rather than air temperature alone, temperatures of 28°C can contribute to elevated heat stress when combined with common tournament humidity and solar radiation levels. As a result, this threshold provides a practical indicator of conditions that may increase heat-related challenges for players, even when official WBGT-based intervention thresholds have not been reached.

Precipitation Analysis

Daily precipitation data were obtained via the Open-Meteo Historical Weather API (Zippenfenig, 2023), which serves ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) at 0.25° (~25 km) resolution for the period 1940-present. For each tournament city, daily precipitation totals in millimeters were extracted for the nearest available grid cell. We calculated total precipitation, average daily precipitation, and the number of heavy rainfall days during each tournament window for every year between 1970 and 2025. Heavy rainfall days were defined as days receiving 10mm or more of precipitation, consistent with the World Meteorological Organization (WMO) definition of a heavy rainfall day. Unlike the temperature analysis, no counterfactual precipitation dataset was used; precipitation results therefore reflect observed trends only and do not include climate change attribution estimates.