Celsius.
Wednesday is expected to see a Wimbledon record high of around 35 degrees which would require the heat index, where matches are briefly suspended, to be consulted.
Organisers say the heat rule, which allows for a 10-minute break between the second and third sets of women’s matches, can be used when temperatures rise above 30.1 degrees Celsius.
However, the rule which has been adopted by Wimbledon after lobbying from the WTA, does not apply to men even though they have to slug it out over the best of five sets.
The highest-ever temperature recorded at Wimbledon was 34C in 1976.
Nadal, who lives in sun-kissed Mallorca, said he would be happy to see the sun keep shining.
“In Australia it can be much, much worse so it’s no comparison but actually it’s beautiful,” said the Spaniard.
“When you have this weather here in Wimbledon it’s probably one of the best places in the world.”
French 13th seed Jo-Wilfried Tsonga was probably wishing for a few clouds after he spent more than four hours to see off Luxemburg’s Gilles Muller 7-6 (10/8), 6-7 (3/7), 6-4, 3-6, 6-2.
Joining Kvitova in the second round was 10th seeded German Angelique Kerber who handed compatriot Carina Witthoeft a 6-0, 6-0 drubbing.
Kerber, a semi-finalist in 2012 and who won the Birmingham tournament on grass in the run-up to Wimbledon, took just 45 minutes to clinch victory, firing 21 winners past the world number 53.
It was the third so-called “double bagel” result of the women’s first round.
Later on Tuesday, 2013 champion and home favourite Andy Murray takes a 2-0 career lead over world number 59 Mikhail Kukushkin into their opener on Centre Court.
Like Murray, Kukushkin is coached by a woman — his wife Anastasia.
Murray beat his rival twice in 2012 at Brisbane and then at the Australian Open in the fourth round.
That remains Kukushkin’s best run at a major although he did reach the third round at Wimbledon in 2014 where he lost to Nadal.