Forecasters are warning there may be significant falls of up to 80mm in lower-lying parts of the Horowhenua Kapiti Coast and North Taranaki.
People in these areas have been advised to watch for rapidly rising rivers and streams, and possible surface flooding and slips.
Although the warnings do not cross into eastern regions, today's one-day cricket international in Napier may still be a casualty of the wet weather.
Napier is expected to swelter on a sticky 27C but rain is predicted across the city throughout the day. It should clear this afternoon, but forecasters are predicting rain to return in the evening during the second innings.
Gale-force winds are likely to start around lunchtime in Wellington and last until midnight.
Those heading to the Guns N' Roses concert should be prepared for heavy rain and blustery gales.
The slow-moving front bringing the wet weather to the lower North Island is expected to weaken and head north on Friday.