Data story · Weather
Which cities are warming fastest?
Fit a straight line through 25 years of average temperatures for each of the 193 cities in Huezle and 174 of the lines slope upwards. The steepest run through Toronto and central and eastern Europe.
Every strip on this page is a real Weather strip from the Huezle app, drawn by the app’s own code. More about Weather.
How to read the strips
Each strip is one city, with one band per year from 2001 on the left to 2025 on the right. A band is coloured by that year’s average temperature, from Cold through Mild to Hot, on one scale for every city. A warming city drifts towards the warm end from left to right, but subtly: the scale has to cover the Arctic and the Sahara, and a degree or two is a small step on it.
How the trend is measured
For each city we fitted a straight line by least squares through its 25 yearly averages. The slope, in degrees Celsius per decade, is the trend. The temperatures come from NASA POWER, a gridded dataset built from satellite observations and a weather model, so each figure is for the city’s grid cell rather than a thermometer in town. Twenty-five years is short for climate, so read the rankings as what this data shows, not a verdict on any one city.
The fastest: Toronto, then Europe
- Cold
- Mild
- Hot
Toronto has the steepest slope of all 193 cities, 0.97 °C per decade. Its first five years averaged 8.0 °C and its last five 10.4 °C. It also shows how much a short record depends on where it starts: 2003 was unusually cold here, at 6.2 °C, and if the line starts in 2004 instead, Toronto’s slope falls to 0.44 °C per decade.
- Helsinki · 0.87 °C per decade
- Houston · 0.74 °C per decade
- Longyearbyen · 0.66 °C per decade
- Cold
- Mild
- Hot
After Toronto, the next thirteen are all European cities with continental climates, cold in winter and warm in summer, led by Budapest and Helsinki and running through the Baltic capitals, Warsaw, Munich, Vienna, Prague, Berlin and Kyiv. Houston is the fastest-warming US city in the data, 16th overall. Longyearbyen in Svalbard warmed by 0.66 °C per decade, although a cold Arctic town swings so much from year to year that its line is less certain than most.
The overall picture
Across all 193 cities the typical trend is 0.3 °C per decade. It follows climate type: continental cities warmed fastest, with a typical 0.66 °C per decade, and monsoon cities slowest, at 0.18 °C. The years tell the same story without any line fitting. For 81 cities the warmest year in the data is 2024 or ties with it, and for 163 the warmest year is 2015 or later.
The cities that did not warm
- Cold
- Mild
- Hot
Nineteen cities have a downward slope. Several are clustered in northern India and Pakistan, with Islamabad the steepest at −0.76 °C per decade, and Khartoum, the warmest city of all on average, is among them. Others, such as Kampala almost on the equator, are essentially flat.
Read the cooling cities with care. This is what one model-based dataset shows for each city’s grid cell, and it can disagree with the weather stations on the ground. Before quoting a cooling trend for any of these cities, check it against the national weather service’s own records.
For where the heat and cold are greatest, rather than how fast they are changing, see the hottest cities and the coldest cities. The same cities are ranked for wind too, all in the Weather category.
Huezle shows one temperature strip with four cities to choose from. Can you place a city from how cold its bands are?
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Which city is warming the fastest?
Of the 193 cities in Huezle, Toronto has the steepest trend in average temperature from 2001 to 2025, about 1.0 °C per decade, followed by Budapest and Helsinki. Toronto’s figure depends heavily on cold early years; starting in 2004 it falls to 0.44 °C per decade.
How is the warming trend calculated?
A straight line is fitted by least squares through each city’s 25 yearly average temperatures, 2001 to 2025, from NASA POWER. The slope of the line is the trend, given in °C per decade.
Why is Europe warming so fast in this data?
Cities with continental climates, cold in winter and warm in summer, warmed fastest in the data, and central and eastern Europe has many of them. Cities near the equator, where temperatures barely change from year to year, warmed the least.
More guides
- The hottest cities in the world, year by year.Which cities have the hottest days, and which are hottest all year round? 193 cities, 25 years of NASA data, drawn as strips of colour.
- The coldest cities in the world, year by year.Yakutsk drops below −50 °C every winter. The coldest nights in 193 cities, 2001 to 2025, drawn as strips of colour from NASA data.
- The windiest cities in the world.The windiest of 193 cities are all in the Southern Hemisphere, the calmest all in the rainforest. Everyday wind, 2001 to 2025, as strips of colour.
- The cities most often hit by earthquakes and tropical cyclones.Davao and Tokyo lead 58 cities for strong earthquakes and tropical storms nearby, 2001 to 2025, counted year by year from USGS and NOAA.
Now try naming one yourself.
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