Our Data & Methodology

Every number on this site is computed, not copied. This page explains exactly where each figure comes from, so you can judge - and cite - our data with confidence.

Climate averages (the historical layer)

Each city page shows monthly climate normals built from ten full years (2015–2024) of daily weather history:

• Source: the ERA5 reanalysis dataset, accessed through the Open-Meteo archive API - the same data family used in climate research.
• Resolution: daily highs, lows, precipitation, snowfall, sunshine and humidity for each city's exact coordinates.
• Aggregation: roughly 3,650 daily records per city are averaged into monthly normals.
• What "record high" means here: the highest and lowest daily values in that ten-year window, at that grid point - not an all-time station record. ERA5 is a gridded reanalysis, so its values are smoothed across a cell and can sit a few degrees below a nearby weather station's official extreme. We label these as decade extremes everywhere they appear, because calling them records would overstate them.
• Climate types follow a simplified Köppen classification computed from those normals.

Because the window is fixed (2015–2024), the averages are stable and comparable across every city we cover - they don't drift with each site update. That comparability is what makes the "how this city compares" block on each climate page possible: when we say a city is drier than 94% of our dataset, every city in that comparison was measured the same way, over the same years.

Live conditions and forecasts

• Source: WeatherAPI.com (current conditions, 48-hour hourly, 14-day daily, air quality, alerts, astronomy).
• Refresh: each city's bundle is cached for about 30 minutes, then refreshed on the next visit.
• Freshness labels: every live page shows when its data was last updated; if the upstream feed is briefly unavailable, we show the last good observation and say so.

Rankings

The hottest and coldest lists compare the most recent cached observation for every covered city - a live snapshot, not a climate ranking. No modeled or interpolated values are mixed in.

Editorial content

City and country descriptions are computed from each location's own climate figures by our own software - not written by hand per city, and not produced by a language model. The hottest month named in a city's text is that city's actual hottest month in the data, and every comparison is a real ranking against the rest of the dataset.

Which facts a page leads with depends on what is unusual about that place: a city whose rain falls in three months is described through its wet season, one with a wide annual swing through its seasons, one that barely changes through what changes instead. Two cities read alike only when their climates genuinely are alike.

Guides are a different thing and are handled differently: they are written and reviewed by a person against the primary sources listed at the bottom of each guide (NWS, USDA, FDA, EPA and peers), with a visible last-reviewed date.

Corrections

Spotted something off? Tell us - corrections ship quickly, and the fixed page updates its modification date.