It says the heavy rain might cause streams and rivers to rise rapidly with a possibility of flooding and slips and hazardous driving conditions.
And while the alert extends to 1pm Saturday it warns further bursts of heavy rain might affect this area late Saturday and overnight Saturday.
Thames-Coromandel District Council has issued a warning to motorists telling those travelling into the holiday region up to 130mm of rain and gusty winds was expected to hammer the region from 3am Saturday through to 6am Sunday.
"With our catchments still saturated, it is possible that more slips and surface flooding will occur," it posted on Facebook today.
While wet weather is in store for most of the North Island the South Island will enjoy a spell of dry weather in most parts.
However, MetService is warning the school holidays will have a wintry feel for the south with polar air straight off the Antarctic shelf lingering across much of the country this weekend and into next week with another "bitter outbreak" signalled for Wednesday.
"Current models suggest the cold air moving over the country mid next week has Antarctic origins," the forecaster posted on Facebook.
By Thursday temperatures for most main centres are expected to plummet to single digits with Wellington recording a low of 4C and a high of 9C, while Christchurch is expected to get down to near-freezing on 1C overnight and 10C during the day.
The forecaster said the current model trajectory had the air off Antarctica moving quickly across our shores.