"It's Sunday where things start getting a bit sour, you've got rain developing in the morning."
He said the rain would not be very heavy, but would continue into Monday.
"If people want to have a barbeque, Saturday is the day for it."
He said the temperature would cool down a couple of degrees when it began to rain on Sunday, but it would remain muggy.
He said both Napier and Hastings will have highs of 24C on Sunday and Monday.
"It's cooling down a little bit, but it is still going to be relatively muggy."
Napier will have a low of 15C and Hastings will have a low of 14C on Sunday, while lows will be around 11C or 12C across the region on Monday.
He said it looked like the temperature would begin to pick up again about Wednesday.