About 0.7°F per decade, measured from Aarau's official daily weather records, 1971–2025. Individual years still bounce around — some recent ones came in cool — but the long-term line has clearly risen.
Is that a lot? Aarau's warming is broadly in line with other cities in Switzerland — neither unusually fast nor unusually slow.
What has actually changed
Each card compares the 1970s (the first ten years of the
record) with recent years (the last ten) — the same span
the headline and the chart use.
Freezing nights
7 fewer nights
1970s
70 / yr
→
Recent
63 / yr
Milder winters — fewer frosts
Average temperature
+2.7°F
1970s
50.5°F
→
Recent
53.2°F
A steady upward drift
Hot days above 90°F
8 more days
1970s
4 / yr
→
Recent
12 / yr
More days of serious heat
Rainy days
9 fewer days
1970s
173 / yr
→
Recent
164 / yr
Drier on average
Aarau's temperature, year by year
Average temperature for each year from 1971 to 2025.
a warmer-than-average year a cooler-than-average year
Each bar is one year. Most recent years sit above the older ones.
Some recent years still came in cool — warming is a slope,
not a straight climb.
In day-to-day terms, that long-term shift shows up as about 5 more days above 90°F compared with the 1970s.
When in the year the change shows up
How much warmer each month is now than in the 1970s.
Useful if you garden or care about a particular season —
otherwise the headline above already has the answer.
June has warmed the most — about 2.7°F. The warming runs across the whole year, not just one season.
Methodology & sources
Temperature — the official 1991–2020 climate normals from a national meteorological service, measured at Buchs / Aarau, about 3 km from the city centre.