Heavy rain and flooding has closed State Highway 63 in the upper South Island

The road in the Wairau Valley is shut - bringing the number of closures to four.

Waka Kotahi Top of the South System Manager Andrew James says this means there's no routes between Marlborough and Nelson or from Marlborough to Tasman and the West Coast.

He says a substantial amount of flood debris needs to be cleared before the road can reopen.