Residents are being reassured that a yellow powdery substance appearing in waterways around the Bay of Plenty is nothing to be concerned about.

The Bay of Plenty Regional Council says it has had lots of calls from concerned residents lately.

'We want to reassure you that this happens every year and is actually pollen,” says a post on the council Facebook page.

The pollen season has hit hard and early this year, with many people reporting hayfever symptoms.

According to the New Zealand Pollen Forecast on the MetService, the full pollen season on NZ is about 34 weeks lone and varies in its timings each year.

It can begin in July or August with the Pinus season and continues into August/September with deciduous trees like oaks, elm, birches and other deciduous trees.

'The major pollen hazard, the grasses, dominate in October through to and after Christmas and finally olive trees, privets and chenopod/amaranth/composite weeds contribute to pollen load in January and February.

'Fungal spores are produced into the air in February and March and contribute to ‘hayfever' then.

'In summary, Spring pollens include pine, wattle, alder, poplar, oak, ash, birch and early grasses.

'Summer pollen includes grasses, weeds such as plantains, nettles and sorrels as well as trees such as olive trees and privet.

'Autumn has late grasses, and as vegetation starts to decompose, fungal spores.”