"In the 24 hours ending Wednesday at 8am it was possible a month's worth of rain would fall," Mr Brandolino said.
There would be a bit of a lull in the wet weather from tonight to tomorrow evening when the rain would be more intermittent.
After sunset on Wednesday, the rain would bring 50mm of water down for about 12 hours.
The second round of rain could cause problems with flooding and tree damage, he said.
The second bout of weather could have stronger breezes softening root systems and bring down branches.
Once the last system moved across the country tomorrow night, things would start to settle down again and the weekend was set to have clear weather.
Tauranga City Council emergency management manager Paul Baunton had a standard heavy-rain protocol which was to clear litter and debris from about 200 stormwater "hotspots" before each storm event, and again afterwards.
"Our residents have a part to play too. You can do this by making sure external drains on your property are clear of blockages, and if you see leaves building up in the gutters or sumps in your street, please clear them if you can," Mr Baunton said.
"When driving in the wet, remember to watch your speed and increase your following distance."