The first bite of autumn will be felt over much of the country in the next few days as rain sets in over the South Island.

Today rain is falling over the southern and western parts of the South Island and it was expected to reach the North Island tomorrow, said.

A big drop in temperature was expected to hit later today and tonight across southern regions, and recent daytime high temperatures could be halved, weather analyst Richard Green said.

"Snow can't be ruled out over higher ground and then frosts are a likely scenario in a couple of days time or the weekend."


Another front on Friday could keep those frosts at bay but an anticyclone expected for the weekend should see starry skies and crisp conditions overnight, he said.

Rainfall totals today and tomorrow will vary but the Far North might not see what other parts of the country could be in for, Mr Green said.

Showers were forecast tomorrow morning for the greater Auckland region however they were expected to clear by the afternoon.