Thick fog surrounded much of Hawke's Bay on Saturday but is starting to clear says MetService.
MetService meteorologist Ashlee Parkes said Napier was "very foggy" on Saturday, which only a short period of respite before the fog returned overnight.
"We've had extensive fog formation.
"The ingredients we look for when thinking about fog are clear skies, less winds and sufficient moisture in the lower atmosphere."
She said northeasterly winds on Friday and Saturday had helped send moisture off the ocean into the region, which meant "all those ingredients were there".
Fog was noted across the East Coast from Gisborne down to Wairarapa, she said.
It tended to hand around longer in inland areas like Hastings, in valleys and other sheltered areas but Parkes expected much of the fog to clear by this afternoon.
"Hastings is slowly catching up with Napier this morning."
Hawke's Bay Today understands fog led to at least one flight into the region being diverted from the Hawke's Bay Airport, instead landing in Palmerston North.
However, flights appeared to be operating as expected on Sunday.
Parkes said expected highs of about 15 C and 14 C in Napier and Hastings, with a slightly cooler temperature of 13 C down in Waipukurau.
It would be a "good start" to the week, though a front pushing through early on would bring rain easing to showers on Tuesday
"Most areas should have pretty fine days with a few clouds."