Dehumidifiers—When It’s Raining— what to do
Mould growth is strongly influenced by relative humidity, and keeping indoor moisture levels under control is one of the most effective ways to prevent it from establishing in the first place. As a general rule, mould becomes far less likely to grow when indoor humidity is maintained below approximately 55% (and ideally closer to 45–50%). Once humidity consistently rises above this range—something that commonly happens during periods of heavy rain, high outdoor humidity, or poor ventilation—surfaces and materials inside the home begin to retain moisture for longer periods. This creates the ideal environment for mould spores to activate and colonise.
During wet weather, it is particularly important to reduce the exchange of humid outdoor air with your indoor environment. Keeping windows and external doors closed when it is raining or extremely humid outside helps prevent unnecessary moisture loading inside the home. This is especially relevant in subtropical climates like the Sunshine Coast, where outdoor humidity can remain high for extended periods. Without this control, indoor humidity can quickly climb, increasing the risk of mould development on walls, ceilings, furniture, and stored belongings—and potentially leading to the need for professional mould removal in Sunshine Coast properties.
However, simply closing the home is often not enough on its own. Active moisture removal is usually required to maintain safe humidity levels. This is where dehumidification becomes essential. At Mould Medico, we use and recommend high-performance desiccant dehumidifiers such as the Ion max range, which are designed to efficiently extract moisture from the air even in cooler or low-temperature conditions where standard compressor units can be less effective. These units work by absorbing airborne moisture through a desiccant material, which is then regenerated internally, making them self-sustaining and highly effective for continuous use during extended humid or rainy periods.
Many models in the Ionmax range are also designed with user-friendly controls, allowing homeowners to monitor and maintain ideal humidity levels with ease. Importantly, selected units are recognised under the Sensitive Choice program, endorsed by the National Asthma Council Australia, which supports products that may help improve indoor air quality for people with asthma and allergies.
By combining simple behavioural habits—like keeping the home closed during high humidity—with reliable dehumidification technology, homeowners can significantly reduce the conditions that allow mould to develop, protecting both the property and indoor air quality long-term.