National Asthma Council Australia's winter warning about mould and dust.

The Bureau of Meteorology is predicting wetter than average months for much of southern Australia from July-September.

Higher humidity levels indoors make it easier for mould and dust mites to thrive and when mould is present, tiny spores are released into the air, which can trigger symptoms.

Symptoms can include nose, eye, and skin irritation, sneezing or wheezing, and severe breathing difficulties.

National Asthma Council's Sensitive Choice Program Manager Adele Taylor said mould was a persistent and difficult problem.

"We all know what mould looks like on a loaf of bread or on the grout in the shower, but mould has a habit of hiding and it spreads to places you cannot see," she said.

Mould can thrive anywhere that has excess moisture or low air flow, including built-in wardrobes, bedrooms with ensuite bathrooms, bookcases and compact laundries.

Condensation on the inside of windows is a sign humidity is too high and it is important for families living with asthma to locate and combat mould.

Dust mites are also a common asthma trigger, taking up residence in pillows and mattresses, curtains, and furniture.

While it is almost impossible to get rid of dust mites completely, reducing humidity in the home can help control them.

"People need to know what their asthma triggers are including seasonal changes and have an up-to-date action plan ready to deal with them," Adele said.

For more information on managing asthma, click here.