Record-breaking weather: Why is it so hot?

The lower South Island is sweltering through some of its highest temperatures on record.

In Invercargill on Sunday, it was 32.3degC. The last time it was nearly this hot was in 1921 when it was 32.2degC.

MetService meteorologist Lisa Murray says there are a few different factors contributing to the heat.

"[On Sunday] we had a north-easterly wind across Invercargill which helps, because we had the fern effect where the mountains and the land heat the air before it actually gets to Invercargill.

"On top of a very warm air mass we have a low out to the west, a high to the east and it's pulling down this really warm air from the north. And all that combined with clear skies, plenty of sunshine and we got the record temperature.

Ms Murray said this bout of warm weather all started in mid-November.

"There was that big high that sat over us for three and a half weeks. It was really unusual to get a high that stuck around for that length of time at that time of year. That really started the summer off with warm temperatures across the Tasman Sea and even in our own coastal waters.

She says the effect on the water temperatures have been drastic.

"We had 5-6degC higher than normal in some areas of the Tasman Sea. In our coastal waters it was 3-4degC for some areas as well.

"It's going to have a big impact on life within the sea, and also on weather events. One of the ingredients for these really intense lows is these warmer sea temperatures."

The warm weather is expected to continue.

Newshub.