Rotorua weather analyst Brian Holden said the unpredictable weather is normal, but late for this time of year.
"Winter just hasn't wanted to let go ... we are still getting frosts like we did this week, followed by a glorious day, and now we are going to get some rain."
Rotorua had received about 80mm of rain this month, still less than the average of about 120mm for September, he said.
"The rain fall is normal but just a bit later - it's been in fits and starts."
The dodgy weather is likely to affect crowd numbers at major outdoor events in Rotorua this weekend.
The annual Chinese Mooncake Festival, which last year drew 500 people to see the spectacular costumes, is planned at the Arts Village tomorrow night from 6pm.