Shifting Seasons
Climate change shows up in the calendar. Spring now arrives up to three weeks earlier across temperate regions; autumn lingers longer, with the effect intensifying toward the poles. The data on this page makes the pattern undeniable: year-by-year correlations between seasonal timing and global temperature across 28 countries, a latitude chart spanning the Arctic to the Southern Ocean, a world map of every monitored region, Kyoto's 1,200-year cherry-blossom record, and the US growing season since 1895. Different datasets, different continents, the same story.
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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.
What do the coloured dots on each seasonal bar represent?
Each dot marks one calendar year. Its position along the bar shows how that season's timing shifted relative to the 1991-2020 baseline (earlier to the left, later to the right). Its colour shows how warm that specific year was globally, keyed to the NOAA global surface temperature anomaly scale: deep blue for cooler-than-baseline years through to deep red for the hottest. This lets you see at a glance that the most recent years (the reddest dots) are also the ones with the most shifted seasons, revealing the direct link between overall warming and seasonal timing change. The Auto-Stretch toggle rescales the colour range to the spread within each individual country or indicator, which can make smaller signals easier to read.
Which countries show a shifting wet season?
The wet-season shift chart appears for countries where a distinct rainy season can be identified from the temperature and precipitation record - primarily tropical and subtropical countries across South and Southeast Asia, sub-Saharan Africa, Central America and northern Australia. Temperate countries with year-round rainfall distribution (most of Europe, for example) show the warm-season chart instead. The data source is Copernicus ERA5 via Berkeley Earth country-level aggregates.
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.