Six car crashes occurred in five hours as thunderstorms rattled the region last night.
Eastern District Command Centre Acting Senior Sergeant Clint Adamson said a minimum of six crashes had occurred in the Napier and Hastings areas as weather took a turn for the worse.
Mr Adamson said all of the crashes, in which there were no major injuries, could have been avoided.
"It comes down to people not adjusting their driving [according to the weather]," he said.
Most of the crashes happened in Hastings.
Weatherwatch.co.nz head weather analyst Philip Duncan said the thunderstorms were the result of a low pressure system from the Southern Ocean mixing with warmer air to create unstable conditions.
The thunderstorms happened offshore and there was also a severe hailstorm between Maraekakaho and Tikokino, in Central Hawke's Bay.
MetService meteorologist Nicole Ranger said the cold air moved away last night.
However, rain was expected to persist today. There was a possibility of heavy rain, easing in the evening, and strong southerly winds. Tomorrow, showers would clear and fine spells develop, with strong southerlies easing, Ms Ranger said.
The outlook for the weekend was "mainly fine".
Mr Duncan said although the rain today was due to a cooler weather pattern, the region was seeing above average temperatures. "Normally by now we'd be seeing lows getting closer to zero [degrees] most nights."
The temperatures were part of a neutral weather pattern and the past three years had seen similar temperatures.
"Whether it's connected to global warming, I don't think we'd know that for a long time."
Mr Duncan said there was a fairly high chance we would enter an El Nino system later this year, which would mean more predictable weather patterns. El Nino weather patterns brought dry weather and westerly winds.
"It's too early for them [farmers] to be worried about it, but it's certainly not too early for people to be paying attention," Mr Duncan said.