Polish advice: Keep windows closed during peak heat to avoid indoor overheating

During high‑temperature periods Polish experts warn that opening windows throughout the day can backfire, as hot outside air quickly raises indoor temperatures and turns apartments into a sauna. The most intense heat typically occurs between 15:00 and 18:00, when windows should remain shut and, if possible, covered with curtains, blinds or reflective film to block solar radiation.

Ventilation is still effective if timed correctly. The recommended windows‑open periods are early morning (around 05:00‑08:00) when outdoor air is coolest, and late evening or night when temperatures fall. Creating a cross‑draft by opening windows on opposite sides for a short burst (10‑15 minutes) helps expel stored heat. Additional measures include limiting use of heat‑generating appliances, using fans (optionally with ice‑filled bowls), and keeping blinds or shutters closed on south‑ and west‑facing rooms.

These practices aim to maintain indoor comfort without relying on air‑conditioning during heatwaves affecting Poland.