Massive swells have pushed over seawall blocks on State Highway One north of Kaikoura, delaying the road's opening.
NZTA says big seas overnight have pushed the temporary sea wall blocks onto the road at Ohau Point.
The agency says most of the highway is open on schedule this morning, but it'll stay shut at Ohau until at least 10 o'clock this morning.
It's also warning drivers high tide is due again at 11 am.
Southbound traffic from Blenheim should use the alternate route – SH63, SH6, SH65, SH7 and back onto SH1 at Waipara.