Brera Astronomical Observatory in Milan: The Oldest Weather Station

The oldest weather station in GHCN-daily, which is the data set used at Climate Binge, is the Brera Astronomical Observatory in Milan, in northern Italy. The data for the weather station begins in 1763, when the observatory was under construction. You can view the Milan data in the app here. The next oldest weather station is at the Clementinum in Prague. You can view the Prague data in the app here. Before Daniel Gabriel Fahrenheit invented the first mercury thermometer in 1714, weather data was imprecise. In order to get any data before that, we have to rely on things like tree ring analysis and Antarctic ice core analysis.


By looking at the chart, we can see that the winters of 1834/35 and 1835/36 were particularly long, meaning that the growing season of 1835 was short. These years are examples of the extreme cold weather brought on by the Little Ice Age, which lasted roughly between 1500 and 1900.

Have a look at the zipper line produced by leap days. The data from the Brera Astronomical Observatory is so old that you can see, in the zipper line, where leap days were skipped in 1800 and 1900.