Wet weather's starting to come in now, but there's no need to pack up the tent and go home early.

Rain is falling over the South Island this evening, hitting parts of the North Island overnight, and spreading further north tomorrow.

MetService forecaster Gerard Barrow says high exposed areas will get the heaviest falls, so travellers should be fine if they take care.

"Affecting people mainly doing things in the ranges, maybe trampers. It's probably not going to affect lower lying areas."

Mr Barrow says trampers should stay alert, as the worst of it will hit high exposed areas.

"The problem is that this amount of rain is going to be falling during a relatively short period of time and so that can cause problems, it can cause rivers, streams to rise quite quickly."