You know it's getting hot in Otago when your jandals stick to the tarseal.
It was a problem in parts of Dunedin and Mosgiel yesterday as temperatures soared and records tumbled.
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MetService meteorologist Lisa Murray said it was the hottest January day as well as the ''all-time'' hottest day on record for Dunedin Airport, which reached 35.0degC at 3.12pm.
Records began in 1972. The former record for January was 34.6degC on January 18, 2004, and the former ''all-time'' hottest day was 34.9degC on February 26, 1995.
New Zealand's highest recorded temperature was 42.4degC recorded at Rangiora on February 7, 1973.
By comparision, Auckland's hottest recorded temperature was 32.4degC on February 12, 2009, at Whenuapai Air Base, equalling a high recorded in the Auckland Domain in February 1872.
Dunedin Airport customer services team member Judy King said part of her job yesterday was delivering mail to buildings around the airport. She said the heat radiating off the asphalt was ''pretty intense''.
It certainly felt like one of the airport's hottest days in the 10 years she had been working there, and it was lucky there was a breeze to counter the worst of the heat.
''It's nice to be inside in the air-conditioning, I must say.''
The heat caused ''bitumen bleeding'' in some parts of Dunedin and the Taieri, and the Dunedin City Council maintenance contractors used trucks to spread grit on affected roads.
Hundreds of residents took to beaches and swimming pools to cool off.
Invercargill residents also sweltered, with temperatures reaching 30.3degC. It was the third successive day the temperature had reached the 30s in the South, Ms Murray said.
Southland Hospital reported a spate of visits from residents to its emergency department for heat-related problems, from fainting to kidney trauma.
A Southern District Health Board spokesman said a ''very small number'' of elderly Dunedin and Mosgiel residents presented at Dunedin Hospital's emergency department yesterday with some effects from dehydration, but none were admitted.
Many Dunedin residents had difficulty sleeping on Monday night because the temperature remained so high.
Between 10pm on Monday and 8am yesterday, the temperature dropped to just 22.5degC, which the MetService said was an ''unofficial'' January record.
She said the data had to be checked with several organisations.
The previous January record for ''overnight highest minimum air temperature'' was 18.9degC in January 1995.
Ms Murray said there were three contributing factors to the hot weather over the area yesterday.
''We have a low out to the west in the Tasman Sea and a high out to the east in the Pacific.
''These are like two spinning wheels, dragging down warm air from the north .
''So we have a warm northeasterly flow over the country - a very warm air mass.
''When we have winds blowing over the ranges, down in to coastal areas, we get the foehn effect where the air dries out and heats up.
''The final thing is clear skies and sunshine. All of that combined created the hot temperatures,'' she said.
Tuesday's top temperatures
• Dunedin Airport: 35.0degC - Record
• Alexandra: 32.1degC
• Dunedin City: 32.0degC
• Balclutha: 31.0degC
• Gore: 30.9degC
• Invercargill: 30.3degC
• Queenstown: 30.0degC
• Wanaka: 29.1degC
• Oamaru: 27.4degC
