NZ Transport Agency Waka Kotahi (NZTA) is urging drivers in the Waikato region to slow down and adjust to the conditions, with heavy rain affecting roads and making conditions hazardous for travel.

NZTA says the heavy rain has caused potholes to form at several locations on the Waikato Expressway (SH1), and nose to tail crashes on the highway have caused significant delays for drivers.

Other highways in the region have also been affected by the heavy rain, including a lane closure on SH31 at Kawhia Road - crews are now on site clearing material.

People across the Waikato and Bay of Plenty are urged to to slow down, increase following distances and drive to the conditions.

Watch for surface flooding, slips, and debris and avoid driving through floodwaters.

People can check road conditions before heading out via the NZTA Journey Planner.