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Has the climate in Harpenden changed?
Harpenden has warmed about 1.6°F between 1991 and 2024.
About 0.5°F per decade, measured from Harpenden's official daily weather records, 1991–2024. 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.
Harpenden's temperature, year by year
Average temperature for each year from 1991 to 2024.
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.
Methodology & sources
Temperature — 1991–2020 normals computed from 30 years of daily observations at Northolt, a weather station, about 30 km from the city centre. The underlying daily records come from NOAA's global station network.