Bonn in July: July is the hottest month of the year with the highest heat wave risk, maximum solar radiation, and occasional drought conditions. Bonn on the Rhine has one of Germany's mildest climates thanks to its sheltered position in the Rhine valley. Climate change is leaving visible traces here too — deviations from the long-term mean reveal how weather extremes in Bonn have shifted over the past decades.
July in Bonn typically shows high summer heat, heat wave risk, and dry periods. Deviations from the 10-year average reveal how the local climate is changing.
This page compares the daily measured values of the current year against the average of the last ten years, the so-called 10-year mean. The deviation values in the KPI cards show directly whether the current month is warmer, sunnier, wetter, or windier than usual. The reference data comes from Open-Meteo's ERA5 weather archive and includes daily measured maximum and minimum temperatures, sunshine hours, precipitation totals, and wind speeds.
A ten-year average is short enough to reflect current climate trends, yet long enough to statistically balance out individual extreme years. The World Meteorological Organization (WMO) recommends 30-year normals as the official climate reference, our 10-year mean is deliberately more present-focused and therefore shows the climate change of the most recent decade more clearly.
The daily data for the current year comes directly from Open-Meteo in real time. The reference mean is calculated from actual measured values of the last 10 years, no statistical model, but real historical archive data. The basis is ECMWF's ERA5 reanalysis dataset.
The deviation shows the difference between the current monthly average and the 10-year reference value for the same month. A value of +2.3 °C means: the current month is on average 2.3 degrees warmer than the average of the last 10 years.
Weather review pages are available for over 100 cities in Germany, Austria, and Switzerland. Choose your city from the overview page or use the weather comparison tool on the homepage for custom periods.