Pick your own idea of a pleasant day. This map counts the months in which the average daily high falls inside your band, everywhere on land, for the climate of 1970 to 2000 and for 2041 to 2060. Then search for your city.
Everyone has a private idea of good weather. Mine is a day warm enough to sit outside without a coat and cool enough to walk across town without wilting. A simple way to put a number on that is the average daily high for each month of the year: the typical warmest point of the day. If it sits between 18 and 27 °C (64 to 81 °F), call the month pleasant. Then count.
That count makes a surprisingly vivid map. The tropical lowlands are too hot in every month; the far north is too cold in every month; and the pleasant places are a thin and shifting fringe between them, plus a handful of high tropical cities where it is spring all year. But my band is not yours, so the map lets you set the band yourself, swap between the recent past and the middle of this century, and look at one month at a time.
Drag the two handles to set the lowest and highest average daily high you would call pleasant. Switch between the climate of 1970 to 2000, the projection for 2041 to 2060, and the change between them. Or choose One month to see where a single month falls inside your band. Search for a city, or tap the map, to see its year.
Loading the climate grid (about 4 MB)...
With the default band, the average patch of land outside Antarctica gets 2.5 pleasant months a year in the climate of 1970 to 2000. A third of it (34%) gets none at all, and the reasons split two ways: 12% is too cold even at the height of summer, and 22% is too hot even in the coolest month. Only 8% has six or more pleasant months, and 1.4%, about 2.0 million km², has all twelve.
People are not spread like land. They crowd into the warm middle latitudes and the tropics, so the average person in a city of 15,000 or more gets more pleasant months than the average square kilometre: 3.6. But a fifth of them (21%) live where no month is in the band, almost all because it is too hot: Lagos, Kinshasa, Mumbai, Bangkok, Jakarta and Ho Chi Minh City among the largest.
Where are the pleasant months? Average them by latitude and you get a belt in each hemisphere, between the deserts and the cold. The southern belt is the stronger: with less land and more ocean the southern mid-latitudes have milder seasons, and land between 30 and 35 degrees south (South Africa, Australia, Chile, Argentina, Uruguay) has the most pleasant months of any band of latitude, 5.9 on average.
Twelve pleasant months need a climate with almost no seasons and a warm but not hot day, and on Earth that mostly means altitude in the tropics. Of the 560 cities of a million people or more, 14 had every month in the band in 1970 to 2000: São Paulo, Lima, Addis Ababa, Caracas, Cali, Medellín, Curitiba and others in Brazil, Mexico, Peru, Madagascar, Rwanda and South Africa. Tap one to see its year.
These are also the places where a degree or two matters most. A flat year means every month sits at much the same temperature, so when the whole year warms, months leave the band together. By 2041 to 2060, in the mean of the three models, only 5 of these cities have twelve: Addis Ababa, Medellín and Arequipa keep theirs, and Cape Town and La Paz, cooler today, join them. São Paulo falls from 12 to 8, Lima to 9, Kigali to 4.
WorldClim's projections for 2041 to 2060 take three climate models under SSP2-4.5, a middle-of-the-road emissions path, and downscale them to the same grid. In their mean, the average daily high on land outside Antarctica rises by 2.6 °C over the 1970 to 2000 baseline (the three models give 1.6 to 3.8 °C). The pleasant fringe moves with it.
For people in cities the average falls from 3.6 to 2.9 pleasant months. 46% of them live in a city that loses at least one month and 14% in one that gains, and the share who get none at all rises from 21% to 26%. On land the average falls from 2.5 to 2.2, and the area with all twelve months shrinks from about 2.0 million km² to 1.1 million.
Months are lost at the hot end and gained at the cool end. Across the world's cities, the losses win.
For 65% of people in cities, at least one month that was pleasant becomes too hot; for 40%, at least one month that was too cool becomes pleasant. Many cities do both: the season slides earlier in spring and later in autumn, while the middle of summer leaves the top of the band. In 38 cities of a million or more, one pleasant season splits into two, a spring and an autumn either side of a summer that is now too hot. Paris goes from May to September to May and June, then September and October; Berlin, Toronto, Vienna, Warsaw and Moscow follow the same pattern.
Most people live in the northern hemisphere, so with the default band May is the most widely pleasant month for city dwellers in 1970 to 2000 (49% of them), and July and August, too hot across much of Asia, the Middle East and the American south, manage about a quarter. By 2041 to 2060 April edges ahead (40%) and July and August fall to 14%.
The biggest losers among big cities are in the tropical highlands and the warm plateaus of Africa and South America, where the year is flat and close to the top of the band: Brasília goes from 9 to 0 pleasant months, Bandung from 8 to 0, Kampala from 9 to 1. The biggest gainers are cooler highland cities: Bogotá, today a little too cool, goes from 3 to 11, and Quito from 0 to 4. Countries with cool summers gain too. People in British cities get 3.2 pleasant months on average now and 4.3 by mid-century; London goes from 4 (June to September) to 5 (May to September).
The exact numbers depend on the band, which is why the map lets you move it. The direction does not. I tried seven bands, from a cool 15 to 25 °C to a hot 22 to 32 °C. In every one, the average person in a city loses pleasant months by mid-century, and more people lose than gain.
The models disagree about how much, not which way. Under the default band, the share of city dwellers who lose a month is 38% with the coolest of the three models (MPI-ESM1-2-HR) and 50% with the hottest (UKESM1-0-LL), and between 236 and 278 of the 560 big cities lose at least one. The city profiles above shade the range across the three models.
Climate now. WorldClim 2.1 monthly averages of daily maximum temperature for 1970 to 2000, on a 10 arc-minute grid (about 18 km at the equator), interpolated from weather stations with elevation and other covariates (Fick and Hijmans 2017). A month is pleasant when its average daily high is within the band, inclusive. The default 18 to 27 °C is my choice, not a standard.
Climate in 2041 to 2060. WorldClim's downscaled CMIP6 projections for three models (MPI-ESM1-2-HR, UKESM1-0-LL and IPSL-CM6A-LR) under SSP2-4.5. I average the three models' monthly highs and count months in the mean; the paper and data also give each model separately. This is three models and one scenario, not the full range of possible futures: UKESM1-0-LL is known as a hot model, and a higher emissions path would move things further. The downscaled grids leave out 6.3% of the land area that the baseline covers (coasts, small islands and lake shores); there I add the change from the nearest covered cell, a median of 19 km away, to the baseline.
Cities. GeoNames lists 34,191 places with 15,000 people or more. Each takes the 10 arc-minute cell nearest to its point (a median of 6.7 km away). For population totals I leave out parts of cities (such as boroughs) and historical places, so that people are not counted twice, which leaves 31,778 cities and 3.9 billion people. GeoNames populations mix city proper and wider municipality definitions (Chongqing's 22 million is a whole municipality), so treat population-weighted figures as indicative.
Limits. A 10 arc-minute grid smooths steep mountains and coasts, so a hillside town or a sea-cooled waterfront can differ from its cell. The baseline is 1970 to 2000; the climate has already warmed since. And this is about afternoon highs only: humidity, rain, wind, sunshine and nights are left out, so a humid 26 °C counts the same as a dry one. "Pleasant" is a convenient label for a temperature band, not a measure of comfort.
Land outside Antarctica: 585,546 cells of 10 arc-minutes. Share of land with 0 pleasant months: 34.0% now, 36.7% in 2041 to 2060; with 6 or more: 8.1% and 4.9%; with 12: 1.4% and 0.8%. Land gaining at least one month: 21.3%; losing: 35.3%. People in cities with 0 months: 20.5% and 26.2%; with 12: 3.0% and 1.1%. Cities of a million or more: 264 lose, 71 gain and 225 stay the same. The page's map uses a coarser 20 arc-minute grid; at the default band it gives a land average of 2.51 months against 2.51 on the full grid.