In short: we compare 30 years of average weather for 34,000 cities, month by month, and score how alike two places are from 0 to 100. About 75 or more is a close twin; under 50 is a different climate.

Weather getaway: pick when you travel and the weather you want: a month of your own city's weather, or a preset such as warm and dry (daytime highs about 28 °C / 82 °F, little rain). Pick a month you love at home and the month you want to travel, We compare that one month at home with the travel month everywhere else, to find where your weather is happening. These are averages, not a forecast.

Climate twin: compares the whole year instead, to find the place whose climate is most like yours.

What is compared: daytime highs, night lows, rain and snow, humidity and sunshine. Beach weather only looks at places by the sea. Rain counts on a square-root scale so very wet months do not swamp the score. The typical gaps used are 3 °C for temperatures and dew point, 2.5 √mm for rain and 30 W/m² for sun, weighted 1, 1, 0.7, 1 and 0.5.

Seasons: for places on opposite sides of the equator, seasons are lined up (winter beside winter). You can switch this off under Options.

Travel details: travel times are rough straight-line estimates (about 800 km/h plus check-in, or 80 km/h by road under 500 km). "By the sea" means within about 15 km of the ocean. "Near a major airport" means within about 75 km of a large airport with scheduled flights (OurAirports data, public domain). "Rainy season" flags months with at least 150 mm of rain, or over twice the place's monthly average. Packing tips come from the month's highs, lows, rain and sun. Trip suggestions leave out countries under a US State Department “Do not travel” advisory; always check the latest advisories yourself.

City names: when a suburb is the closest match, the largest city within 45 km is shown instead if it matches almost as well.

Climate data: TerraClimate 1991–2020 monthly normals (Abatzoglou and colleagues, University of Idaho), about 4 km grid, public domain (CC0). Humidity is dew point worked out from vapour pressure; sunshine is solar radiation.

Cities: GeoNames, all cities of 15,000 people or more (CC BY 4.0).

Limits: a 4 km grid can differ from a downtown weather station near coasts, valleys and mountains. The averages describe 1991–2020, not the warmer present. Wind, storms, snow cover and air quality are not included.