People flocked to pools, lakes and beaches across the region as parts of Central and North Otago reached the high 20s and low 30s.
MetService meteorologist Claire Flynn said yesterday was the hottest day of the summer for Dunedin and Oamaru.
While Dunedin's 31degC noon high had almost halved by 6pm, as dark clouds and rain arrived, it meant Dunedin had recorded a hotter day than both Queenstown and Alexandra so far this summer.
Alexandra reached 30degC on January 11, while Queenstown was yet to have a 30degC day, she said.
Sunshine was short-lived for most of the region as a southwesterly took hold about 2pm, sending beach umbrellas and sun hats flying.
The turn was a classic weather pattern for the region at this time of year, Ms Flynn said.
It was unlikely temperatures would reach more than the low 20s in Otago for the rest of the week.
''You could say you had a day of summer.''
Last night police appealed to southern motorists to drive to the conditions, as up to 24mm of rain was expected to fall in the Lakes district, affecting road conditions and visibility.
In Dunedin yesterday a group of volunteer lifeguards gave up their last day before returning to school when St Kilda Lifesaving Club put out a call for extra help on the busiest beach day this summer.
St Kilda Lifesaving Club member Cam Third said about 100 people were in the water during the peak of the heat and the additional help ensured crowds flocking to the beach were safe.
''It's awesome to see that the volunteers are willing to sacrifice their last day off to help out the public.''
