For every city listed here you can compare any two time periods: temperatures, sunshine hours, precipitation and wind. All data comes from the Open-Meteo weather archive.
Each city has its own comparison page, a climate trend page, and for the hand-curated cities a monthly weather review reaching back to 2015. The comparison page sets two time periods side by side, the climate trend page stacks up to ten years of the same month. Which view helps depends on whether you want time comparisons or trends.
The search bar inside any comparison page accepts any city worldwide, not only the ones listed here. The tool currently covers 5,102 cities, of which 102 are hand-curated. Data for all of them comes from the ECMWF ERA5 reanalysis archive via Open-Meteo, day by day from 1940 to today.
For weather across several cities at once, there are region hubs that bundle every city in an administrative unit (e.g. Bavaria, Vienna, Tuscany) onto a single page. Reading a climate trend for an entire region works via the individual city trend pages, because a region hub has no weather station of its own.