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.
