It's been a bad day on the roads around Auckland in the wake of the first major rainfall in some weeks.

Emergency services have been called to crashes in Matakana and Whangaparoa, north of the city, Titirangi, and Te Atatu south.

One of the worst crashes was at Leigh Road in Matakana where a car left the road, leaving three people critically injured.

Police say the rain has led to traffic congestion and a change in road conditions and they're urging extra care.