Weather: MetService explains what's causing recent tornadoes

Tornadoes are incredible forces of nature and they’re also the only known natural enemy of the trampoline.

Since last week, we’ve had two tornadoes reported in Levin and the Kāpiti Coast.

"We are having what's called a major polar outbreak, there's a huge low to the south of the country that's bringing cold air up over the ocean," MetService's Hordur Thordarson said when explaining the rise in tornadoes.

Thordarson told The Project that tornadoes are caused by warm air rising.

"When that gets warm down from below it gets very unstable. The warm air rises and the rising air can spin around and we get these damaging wind gusts."

New Zealand's tornadoes are usually smaller than their American cousins, but these were still enough to cause damage. America gets about 1300 of them a year, Europe around 700.

MetService estimates New Zealand has around five or six tornadoes per year, but they don't have an exact number.

"We actually don't know, because sometimes we have tornadoes where there aren't any observations and sometimes it can be tricky to decide whether it was a tornado or whether it was simply a very strong wind gust."

Thordarson said because tornadoes can be extremely dangerous, it is important to keep safe.

"The best thing you can do is seek shelter, you want to be away from windows that can be broken by strong wind gusts."