Shifting Seasons
Climate change shows up in the timing of the year. Spring arrives earlier, snow leaves sooner, and the growing season stretches. This page pulls together the longest, cleanest records of that shift: a global analysis of hundreds of regions, Kyoto's 1,200-year cherry-blossom archive, the Northern Hemisphere snow record, a live US spring tracker, and the US growing season since 1895.
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FAQs
FAQs
What does the shifting seasons page show?
How the timing and length of meteorological seasons have changed under climate change - when spring now begins, how long summer lasts, when winter snow cover starts and ends, and how these shifts vary by hemisphere and by country. The live charts and the country comparison panel above carry the current values.
How are season-shift indicators measured?
Spring onset uses the USA-NPN Spring Leaf and Bloom Index (USA) and equivalent phenological and temperature-threshold indicators elsewhere. Growing-season length uses the first and last date with daily mean temperature above a region-appropriate threshold. Snow cover uses the Northern Hemisphere snow-cover extent series from Rutgers University Global Snow Lab.
Where does the seasonal data come from?
USA: NOAA NCEI nClimDiv, USA-NPN, EPA Climate Change Indicators. Northern-Hemisphere snow: Rutgers Global Snow Lab. Country-level seasonal anomalies: Berkeley Earth, Copernicus C3S / ERA5. UK seasonal anomalies: Met Office HadUK-Grid.
What baseline is used?
Anomalies are calculated against the 1991-2020 climate normal where available (WMO standard). Some indicators (snow cover, US growing season) use longer reference periods set by the source agency; the baseline is labelled on each chart.
Are summers getting longer?
Yes. The growing season - the run of days with mean temperature above a region-appropriate threshold - has lengthened across most of the Northern Hemisphere since 1970, with the sharpest gains in the contiguous United States and northern Europe. The exact change for any one country, US state or UK region is shown live on this page in the season-length chart and the country comparison panel above; we do not bake numbers into this FAQ because they refresh annually.
When does spring arrive now compared with the past?
Spring is arriving earlier across most of the temperate Northern Hemisphere. The USA-NPN Spring Leaf and Bloom Index (USA), Met Office HadUK-Grid temperature thresholds (UK) and Berkeley Earth / Copernicus ERA5 (rest of the world) all show first-leaf and first-bloom dates trending earlier by roughly one to three weeks since 1980, depending on the region. Pick a country in the country comparison panel above to see the live spring-onset anomaly.
Why are seasonal shifts a useful climate indicator?
Annual mean temperature can mask big within-year changes. Earlier spring leaf-out, longer frost-free windows, later first-snow dates and shorter snow-cover seasons all change the environment for crops, pests, pollinators and water supply long before the headline temperature anomaly looks alarming. They are also independent of the choice of climate baseline, which makes them a good cross-check on the temperature record.
How often is this page updated?
Annual indicators (growing-season length, snow-season length) refresh once a year as the source agencies publish them. Monthly indicators refresh on the same monthly cadence as the rest of the site, typically in the first half of each month.