Reduce sunlight entering rooms during hot weather

Direct sunshine can warm a room and the surfaces inside it, adding to indoor heat. The World Health Organization (WHO) advises covering windows with blinds or shutters during the day when outdoor temperatures are higher than indoors, and opening windows after dark when outdoor air is cooler than indoor air. This is one part of a wider plan for hot weather, not a guarantee that a home will stay cool.

If shading and night ventilation do not keep your home cool, WHO recommends spending 2–3 hours during the day in a cool place. This may be an option when your home is especially hot; consider what is practical and accessible for you. WHO also advises avoiding strenuous activity during the hottest part of the day, seeking shade outdoors and staying informed about official heat warnings.

A practical sequence

1. Notice which windows get direct sun. Consider how exposure changes across the day; not every window needs the same approach.
2. Before sunlight heats a room, close its blinds or shutters. Keep windows closed while outdoor air is hotter than indoor air, especially on sun-exposed sides.
3. Reduce extra indoor heat. Switch off electrical devices that do not need to be on, as WHO advises.
4. Compare indoor and outdoor conditions after dark. If outdoors is cooler, open windows to let night air in. Close them again when outdoor air becomes warmer than indoors or direct sun returns.
5. Understand the fan advice. WHO advises using electric fans only when temperatures are below 40°C, noting that above 40°C fans will heat the body. This guidance does not mean a fan must never be used or cannot help in any circumstances. In extreme heat, prioritise other WHO cooling advice, such as going to a cool place, taking a cool shower or bath, or wetting your skin with a damp cloth, spray or wet light clothing.
6. Keep a wider heat plan in view. Seek shade and avoid strenuous outdoor activity during the hottest part of the day. Regularly check on people who may be more vulnerable, including people over 65, those with heart, lung or kidney conditions, people with a disability and people living alone. These are examples, not a complete list.

Putting it into practice

If afternoon sun falls on a bedroom window, close its shutter before the room begins to heat up and keep the window shut while the air outside is hotter. Later, compare indoor and outdoor conditions. If night air is cooler, open the window to ventilate; close it again as outdoor air warms. If the home remains hot, consider spending 2–3 hours during the day in a cool place. Timing and options will vary with the weather, the room and what is accessible to you.

Limitations to keep in mind

Shading and ventilation cannot guarantee a cool home, and night air may not be cooler than indoors. Homes differ in sun exposure and how they retain heat. This advice does not replace an outdoor heat plan or individual medical advice. People at greater risk, including those with existing health conditions, disabilities or limited support, may need additional help during hot weather. A healthcare professional can help with individual planning.

This article is general health information and does not replace an individual medical assessment, diagnosis or treatment plan.