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Has the climate in Alton changed?
Alton has warmed about 3.9°F since 1971.
About 0.8°F per decade, measured from Alton'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.
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.
Alton's temperature, year by year
Average temperature for each year from 1971 to 2025.
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 24 fewer freezing nights a year and about 6 fewer 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.
January has warmed the most — about 2.8°F. The warming runs across the whole year, not just one season.
Methodology & sources
Temperature — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Alton - Melvin Price L&d (NOAA GHCN station USC00110137), about 4 km from the city centre.