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A 140-year tally of record-hot versus record-cold days. Every day, each of 29 long-running Swedish weather stations can set a new record high or low for that calendar date — and counted across more than a century, the balance between them is a fingerprint of a warming climate.
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Sweden’s temperature wound into a spiral: each loop is one year of daily values. The distance from the centre is the actual temperature — the centre is cold (deep winter), the outer edge is warm (high summer) — so every loop traces the seasonal cycle. The colour is that same temperature, diverging at 0 °C (freezing): blue below zero, red above. It draws day by day, and the loops creep slowly outward as Sweden warms. Switch between daily-maximum and daily-minimum.
Actual daily temperature (Sweden mean across stations, 21-day smoothed) over 1884–2025; radius and colour are both real °C, diverging at 0 °C. Rings mark every 10 °C. In the Seasons view the four shaded wedges mark the seasons — winter at the top (coldest, innermost), then spring, summer and autumn clockwise; switch to Plain for the original unshaded animation. The seasonal balance of records is tallied in “By season” below.
Hot records (above the axis) versus cold records (below), summed over all stations each year. In a stable climate both would shrink toward zero and stay roughly equal. Instead, recent years are dominated by heat.
Hot and cold daily records grouped by decade, with the hot:cold ratio above each pair.
The same hot-versus-cold tally split by meteorological season. Each pair compares the hot:cold record ratio in the first years of the record with the most recent equal-length window.
Reconstructed nationwide mean temperature, with the long-term linear trend.
The stations behind these records — long records reaching back to the 1880s, spread the length of the country. Squares mark stations whose early history is extended with a nearby companion station.
Everything here is built from SMHI open data — daily maximum and minimum temperature for 29 long-running weather stations, most with records reaching back to 1884. SMHI quality-controls these daily series but does not homogenize them, so we apply our own homogenization (correcting for station moves, instrument swaps and the like) before counting records. The series are pulled from SMHI’s open-data API (daily minimum = parameter 19, maximum = 20).
Why 29, when SMHI’s national temperature uses more? SMHI tracks Sweden’s mean temperature from a wider long-record network — historically about 35 stations reaching back to 1860–1889, now a larger homogenized set. That set is built for a homogenized monthly mean with even geographic spread, so it includes several lighthouse and coastal stations whose daily max/min series only begin around 1924. Counting daily records instead needs a long daily series — so we keep the 29 stations with the longest continuous daily min/max (most reaching 1884; a few — Uppsala, Karlstad and Falun — with their daily extremes resuming a little later) and leave out the lighthouse and coastal stations whose daily data begins only in the 1920s.
The 29 stations split into Sweden’s three macro-regions — Götaland (south, 13 stations), Svealand (central, 6) and Norrland (north, 10). The map shows the 29 stations coloured by region; pick a region below to see its records year by year and by decade.
The reconstructed change in mean temperature across Sweden — the recent period (2015–2025) minus the early one (1885–1895) — with its 95% credible interval. Every part of the country warmed (nowhere cooled); the map extends a little beyond Sweden over the surrounding land and sea. Switch between daily-maximum and daily-minimum.
Hot and cold record counts and their ratio, latest years first.