If you've been wondering why you've been suddenly sleepless, ask the weather experts.

Overnight temperatures have been 3.2C hotter than normal in the first two weeks of February forcing many people to resort to fans or air conditioning to help them sleep at night.

NIWA forecaster Chris Brandolino said the minimum daily temperature, which was typically overnight temperature, for the first 13 days of February was 18.7C - 3.2C above average.

"That's well, well above normal," he said. "The water temperature is well over 20C so when you have the air coming off the water it will keep you warmer at night."


The mean maximum air temperature over the first 12 days of the month was 24.7C, 0.7C above average, he said.

Mr Brandolino said weather maps from the last two weeks showed there had been lower pressure than normal and winds from the north and northeast.

He said the region usually had a fair amount of wind which came from the easterly direction which would have been pushing up temperatures.

"Because of that it's going to keep you warmer at night. It's coming off water that's 21C, 22C or 23C. It's going to keep you warm and humid, especially northeasterlies."

In the first 12 days of February, 43mm of rain had fallen.

"It's about spot on in terms relative to the month. That's 49per cent of normal. In a typical February month you'd get 86mm of rain."

In January the average minimum temperature was 17C which is 1.9C above average.

Mr Brandolino said said the forecast for the northern part of the North Island, which included the Bay of Plenty, was for temperatures to be above average for February, March and April.

There was an equal chance of rainfall being near normal or below normal, he said.

Gate Pa resident Hannah Ouellet said she had been struggling to get a solid night's sleep because of the heat. "You definitely wake up a few more times at night than you usually do. You have to have a fan or open the windows."

The 18-year-old said she usually opted for an open window "and then have one leg awkwardly sticking out".

"My dad has never had to use a fan to sleep before but he's got one out this year."

Aircon Tauranga sales manager Andrew Stockman agreed the heat, especially in bedrooms, had been "unbearable".

"Sleep is not as good as it should be and people have been tired and grumpy."

He said demand for air conditioning units was well above normal this year.

The company had already sold about 50 units for existing houses since mid-January, slightly more than double the amount sold in the same time last year.

"I've been pretty much just on the go all the time," he said. "It's warmer than normal and muggier as well."

Mr Stockman said it may be because the heat had lasted longer than usual so people had decided to do something about it.

Smart Sparx Electrical director Hayden Barnsdall agreed his company had also been a lot busier this summer.

Tips for keeping your house cool:

* Try to create a cross draft by opening windows throughout the house. Closing curtains will also keep the sun out.

* Ceiling and floor standing fans are relatively cheap to buy and install, and are cheaper to run than air conditioning.

* Think about planting deciduous trees on the north and west of the house to provide shade in summer. If you don't have trees, eves or roof overhangs stop sun entering the house.

* Try using the fan-only setting on air conditioners which can help create cross-draughts in your home.

* Use the dehumidifying mode - if it's the humidity rather than the temperature that's the problem. Shut your doors and windows in the rooms you're dehumidifying.

- Energy Efficiency and Conservation Authority