Our data & sources
Every number on WeatherChirp comes from a named, public source — and some describe a single city while others describe its whole country.
Measured at each city — its climate and its size.
A national figure shared by every city in the country — so “Safe” or “High income” really filters by the country's rate.
City-level data
7· 30-year ERA5 averages, not a forecastAverage temperature per month, plus daily highs, lows and the percentile range most days fall in.
ERA5A 0–10 score per month blending temperature, rain and humidity into one “how nice to visit” number.
DerivedA dew-point comfort band per month — Dry through Comfortable to Miserable.
ERA5Monthly rainfall, sunshine hours, cloud cover and wind, on city pages and Compare.
ERA5Sunrise, sunset and daylight, computed astronomically for the city's exact coordinates.
AstronomicalCity population, banded Megacity (5M+) → Small (50k–250k). Every city over 50,000 is included.
GeoNamesLatitude and longitude — places each city on the map and powers “nearest to you”.
GeoNamesCountry-level data
8· coverage varies; pages show only what existsThe continent each country sits on.
GeoNamesGDP per capita, banded High → Low. Our own GDP bands for browsing, not the World Bank's official classification.
World BankNational homicide rate per 100k, banded Very safe → High risk. A country-wide figure, not a neighbourhood one.
World BankUS State Department level, 1 (normal precautions) to 4 (do not travel).
US State DeptWorld Happiness Report ladder score, 0–10.
World HappinessHow expensive the country is versus the US (US = 100%).
World BankShare of the population using safely managed drinking water.
WHO / UNICEFSocket types, voltage and frequency, so you know what adapter to pack.
ReferenceSources & licensing
Climate — modified Copernicus Climate Change Service information (ERA5, produced by ECMWF); neither the European Commission nor ECMWF is responsible for any use of it.
Cities — names, locations and populations from GeoNames (CC BY 4.0).
Travel facts — World Bank, US State Department, World Happiness Report, WHO / UNICEF.
Climate figures are 30-year averages (the 1991–2020 climate normal), not forecasts. Income and Safety bands are simplified for browsing, not official classifications. More on how it's built on the About page.