US Open tennis fans are gearing up for the most anticipated match of the tournament so far with Serena and Venus Williams set to meet for the 30th time and extend a sibling rivalry that has endured for two decades.

The pair will face each other for the sixth time at their home Grand Slam on Friday, but will be spared the searing heat that has marked the opening days of the tournament when they step onto the Arthur Ashe Stadium court.

Tournament officials said there was no heat rule in effect on Friday for the first time in three days, with cloud cover expected to bring cooler temperatures.

Serena leads 16th seed Venus 17-12 in their head-to-head record, but most recently lost to her older sister at Indian Wells in March.

Seventeenth seed Serena, however, defeated Venus in straight sets in the 2017 Australian Open final, their last Grand Slam encounter.

With 23 Grand Slam singles titles to her name, Serena came to this year’s tournament in search of a seventh US Open title.

Third-seeded Sloane Stephens is continuing the defence of her US Open title against twice Australian Open champion Victoria Azarenka of Belarus, who leads her American opponent 3-2 head-to-head.

Fans and players can expect much-welcomed cloud cover and cooler temperatures, with a high of just 24.4C according to the National Weather Service.

Tournament officials had imposed a heat rule on Tuesday, Wednesday and Thursday in an effort to relieve players from the sweltering temperatures, but had not implemented the measure on Friday morning.

Several players were forced to retire from play due to heat-related issues during the week, as temperatures climbed above 32.2C.