The mercury dropped to a balmy 24.8C at 7.30am yesterday, making it our sixth highest minimum temperature in the past 50 years.

The hot night was 14C above the monthly average.

The city started to cool down in the early afternoon, with the temperature dropping to 19C at 3.30pm - 20C cooler than the same time on Monday - bringing with it a welcome dumping of rain.

Weatherzone meteorologist Brett Dutschke said conditions were warm across the state, and records were broken in Maryborough, Shepparton, Stawell, Tatura and Yarrawonga.

Melbourne had its equal warmest night in history, the hottest since February 1, 1902, when the record of 30.6C was set.

"To get warm nights is expected, but it does not happen every year. It happens once in every eight to 10 years. Many people would only experience nights like that a couple of times in their lifetime," Mr Dutschke said.

Ballarat's hottest night was on January 18, 1959, when the mercury did not go below 26.9C.

On Monday, thousands of people flocked to Eureka Swimming Pool, making it one of its busiest days this summer.

Staff member Richard Zelencich said the pool was open until 8.30pm.

Patients, staff and visitors at Ballarat Base Hospital were not so fortunate yesterday, with a faulty air-conditioning system.

"The system functioned at a reduced level until it was restored to full capacity early yesterday afternoon. In the meantime, all available cooling was directed to patient areas to maintain patients' comfort and well-being," a spokesperson said.

Weatherzone is predicting possible showers today with a top of 22C. Sunshine is expected tomorrow, Friday and Saturday, before rain on Sunday and Monday.