A lack of rainfall combined with warm weather has led to toxic algal blooms in two North Island waterways, making them unsafe to use.
The Greater Wellington Regional Council says the toxic algae levels in the Waipoua River near Masterton are high, and clumps have been washing up along the river's banks.
The council has posted signs warning of the danger and suggesting river users stay away from the water, especially if they have dogs.
In Hawke's Bay, Lake Tutira has been ruled off limits because of the discovery of potentially toxic cyanobacteria.
