More weather from the Tasman Sea meant temperatures would rise, especially overnight, he said.
Overnight lows were expected to be 12C on Friday, 8C on Saturday and 10C on Sunday, with daytime highs of 18C on Friday, 17C on Saturday and 18C on Sunday.
Earlier this week, overnight temperatures dropped to 5C in Whanganui, with Monday and Tuesday reaching a maximum daytime high of 14C.
“We are now looking at temperatures quite a few degrees above average for a typical August day,” Corrigan said.
Rain overnight on Friday would be coming “from higher than your typical cloud”.
“It’s going to be a question of how many of those raindrops make it down to the surface.
“Most will be evaporating on the way down. The technical term is virga.
“The main rain will be on Saturday morning - around the time people are waking up - but it should be gone by midday.”
There could be longer periods of rain inland, in places such as Hunterville and Taihape.
“The cloud will stick around for a while and then we’ll see skies starting to clear out a bit more in the afternoon,” Corrigan said.
“Contrary to the name, Sunday is going to be cloudy.
“There will be an increase in greyness. First of all, there will be thin, wispy cloud in the overnight period and that will be thickening up.
“It won’t be wet though.”
Corrigan said temperatures next week would be even warmer.
“We’ll see northerly winds and warmer air flow.
“That could take things to 19C on Monday, Tuesday and Wednesday.”
Mike Tweed is a multimedia journalist at the Whanganui Chronicle. Since starting in March 2020, he has dabbled in everything from sport to music. At present his focus is local government, primarily the Whanganui District Council.
