About the weather data
Monthly averages
Our monthly pages use completed years from 1990 to 2025. We calculate each year's monthly average daily high and low temperatures, count its sunny and rainy days, and sum its precipitation. We then average those monthly values across years, giving each year equal weight.
The current, incomplete year stays separate in the daily calendars. All four cities use the same historical period for comparisons.
Typical ranges
The ranges show the 10th to 90th percentiles of yearly monthly values, using linear interpolation. This describes the middle 80% of years, rather than individual daily extremes. Historical averages and ranges are not a forecast for a particular trip.
Sunny, rainy and snowy days
A snow day has at least 0.5 cm of snowfall. Otherwise, a rain day has at least 1 mm of precipitation. A dry day is classified as having no sun when its solar radiation is below 60% of the clear-sky estimate. All remaining days are classified as sunny. Each day has one classification.
Sunny-day counts describe this classification, not hours of uninterrupted sunshine. Precipitation totals include all precipitation, including snow's water equivalent.
Source and geographic resolution
Weather data comes from Open-Meteo's historical weather API. Rain, snow and solar radiation use ECMWF ERA5 reanalysis on a roughly 25 km grid. Temperatures use the finer ERA5-Land data through the ERA5 seamless model.
These are model estimates for the area around each city. Local showers and conditions in hills or on individual beaches can differ. Maps highlight each city's district to show where it is; the figures describe the city itself, not the whole district.
The map coastline and districts come from Natural Earth, whose map data is public domain.
Updates and attribution
Historical snapshots are scheduled to refresh weekly. Published historical pages pick up those changes on the next deployment. Current-year calendars request new data with a six-hour cache; the source archive runs several days behind.
Source weather data is licensed under CC BY 4.0. We calculate classifications, averages and ranges, and round values for display.