|2018 US Open|
|Venue: Flushing Meadows, New York Dates: 27 August-9 September Coverage: Live radio coverage on BBC Radio 5 live sports extra; live text commentaries on the BBC Sport website|
US Open quarter-finalists will have to contend with more heat and humidity on Tuesday, a day after tennis' biggest names toiled in the conditions.
Six-time winner Serena Williams and defending champions Rafael Nadal and Sloane Stephens are all in action on Tuesday, when temperatures are expected to reach 34C in New York.
Wimbledon champion Novak Djokovic struggled on Monday and Kei Nishikori said the heat "really hit him".
He added: "Glad I won in three sets."
Djokovic also came through in three sets against Portugal's Joao Sousa, despite coming off court for medical treatment, and Japan's Nishikori, overcame Philipp Kohlschreiber of Germany.
- Djokovic into quarters despite medical treatment
- Osaka willing to 'break leg' for win
- Murray reaches US Open doubles last eight
Women's world number 36 Lesia Tsurenko also suffered in the conditions during her win over Czech teenager Marketa Vondrousova.
The Ukrainian said: "I was really dizzy and I asked nature or God or somebody, 'please move the shade over faster'."
American Stephens continues her defence on Tuesday against Latvia's 19th seed Anastasija Sevastova, which begins under the midday sun on Arthur Ashe.
That will be followed by Argentine Juan Martin Del Potro's contest against another American, and Wimbledon semi-finalist, John Isner.
Williams and Nadal will take to the main stage at Flushing Meadows in the later session. Williams, 36, is up against Karolina Pliskova at midnight BST before Nadal takes on fellow French Open finalist Dominic Thiem.
The American has only twice played Pliskova in her career. The last time they met was at the 2016 US Open semi-finals when the Czech player came through in two sets.
"She came out strong and she came out very well," said the 23-time major winner. "I have watched her a great deal since then.
"I have taken a lot from that match and I think we are in different positions now. It will be an interesting match."
Williams and Stephens will face each other in an all-American semi-final if they both win on Tuesday.