Dozens of beaches across Auckland are currently unsafe to swim in following bouts of heavy rainfall over the past few days.

Safeswim's website has marked nine beaches as "very high risk", where wastewater overflow has been detected - including Mission Bay, St Heliers and Herne Bay.

More than 20 have been marked as "high risk", which means the levels of faecal indicator bacteria has breached national guidelines for swimming.

Takapuna, Bayswater, Cockle Bay and Titirangi beach are among those.