A severe weather watch has been issued by Metservice, with heavy rain set to hit the Bay of Plenty region, including Rotorua on Wednesday.
Meterologist Tom Adams said Wednesday would be the "worst of the week."
Today, there would be fine spells later on, with a high of 16C and a low of 5C overnight.
On Tuesday there will be showers, Mr Adams said, leading into Wednesday.
"Thursday will have showers which will then clear up."