Data & Methodology

Monthly climate normals

Our primary source is the WMO Climatological Standard Normals 1991–2020, the official 30-year averages reported by national meteorological services and distributed by NOAA's National Centers for Environmental Information (NCEI). Around 270 of our cities use values from an official weather station.

We match each city to its nearest station with two quality filters: the station must be within 25 km of the city, and its elevation must be within 300 m of the city's elevation. The elevation filter matters — a lakeside town matched to a mountain-summit observatory would show absurdly cold values, so such stations are rejected even when they are geographically close.

Where no suitable station exists, we fall back to CHELSA v2.1, a peer-reviewed 1-km-resolution downscaled climatology (1981–2010) widely used in climate research. For a small number of island destinations where 1-km grid cells are dominated by ocean, we instead use the official station normals published by the respective national weather services.

Real-time temperatures and anomalies

Daily forecast highs come from MET Norway's Locationforecast API (CC BY 4.0), collected once per day for every city. The heat anomaly you see is simply today's forecast high minus the city's 30-year average high for the current month — a transparent, reproducible calculation.

These daily observations are archived, which powers the per-city 'recent heat vs normal' history you see on city pages.

Travel verdicts

Ratings like 'Great' or 'Challenging' are computed by a deterministic formula that prefers daytime temperatures near 23°C and low rainfall. No language model is involved in generating any climate figure or verdict — every sentence is a template filled with real data, so the same data always produces the same words.

Limitations

Climate normals describe typical conditions, not guarantees — any individual month can deviate substantially, and a changing climate means recent years often run warmer than the 30-year baseline. Use the figures for planning, and check a short-range forecast close to your travel dates.