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Vienna sits at the crossroads of Alpine and Pannonian climate influences. The Danube Valley channels cold Alpine air in winter and warm air from the Hungarian Plain in summer, giving Vienna more temperature extremes than Western European capitals. Summer highs reach 28–30°C; winters regularly drop below freezing.
The Föhn — a warm, dry wind from the south — is Vienna's most distinctive ventilation event. It can raise temperatures by 10–15°C in hours, sometimes creating unseasonable warmth even in winter. Föhn days bring excellent air quality and dramatic Alpine views visible from the city. Austrian ventilation culture mirrors Germany's: Stoßlüften (burst ventilation) is the norm over tilted windows left open all day.
Vienna's outdoor air quality is among the best of any European capital (AQI 15–30). Pollen is significant from March through July, with birch, grasses, and late-summer ragweed being the primary concern for allergy sufferers deciding whether to ventilate overnight.
In July, the warmest month in Vienna, afternoons reach 28 °C on average and nights fall to 18 °C. The coolest air arrives between 04:00 and 07:00 (18 °C on average): that is when opening the windows cools the home fastest.
In January, the coldest month, air the rooms for 5–10 minutes around 14:00, the mildest hour (4 °C on average). Average humidity is 79%, so short, wide-open airing keeps condensation and mould away without losing much heat.
Fine particles (PM2.5) are usually lowest around 16:00 (9 µg/m³) and highest around 22:00 (14 µg/m³).
| Month | Avg high | Avg low | Humidity | Coolest hours | PM2.5 |
|---|---|---|---|---|---|
| January | 5 °C | -1 °C | 79% | 07:00–10:00 | 16 |
| February | 8 °C | 1 °C | 73% | 06:00–09:00 | 16 |
| March | 12 °C | 2 °C | 65% | 06:00–09:00 | 14 |
| April | 15 °C | 6 °C | 66% | 05:00–08:00 | 9 |
| May | 20 °C | 10 °C | 66% | 04:00–07:00 | 8 |
| June | 26 °C | 16 °C | 63% | 04:00–07:00 | 7 |
| July | 28 °C | 18 °C | 61% | 04:00–07:00 | 6 |
| August | 27 °C | 17 °C | 64% | 04:00–07:00 | 8 |
| September | 22 °C | 13 °C | 72% | 05:00–08:00 | 8 |
| October | 16 °C | 8 °C | 77% | 06:00–09:00 | 10 |
| November | 9 °C | 3 °C | 83% | 06:00–09:00 | 15 |
| December | 5 °C | 0 °C | 84% | 06:00–09:00 | 19 |
Data: Open-Meteo historical archive, hourly averages 2021–2025 (air quality 2023–2025), local time.
How to air your home in winter in Vienna without condensation and mould →
In Vienna, the best ventilation times are typically early morning (5–8 AM) and late evening (after sunset) when outdoor temperatures drop below indoor levels.
Yes, in most weather conditions. Open windows can drop indoor temperature by 2–5°C in 30 minutes if outdoor air is cooler. Check the live recommendation above for tonight.
Above 80% humidity, opening windows can make indoor air feel sticky. Combine with dehumidifier or wait for drier hours.