Graphs and lists of daytime temperatures in Nice, France, since 8 January 1994 – an example of data re-use.
The solid purple line shows a sine function that passes through the highest (27°C) and lowest (13°C) average daytime temperature. The other lines show actually measured temperatures.
These graphs are derived from data provided by CNN, Accuweather (former RainOrShine), Weather-Underground, and the NOAA, four information providers that provide daily weather data. Every day, a robot automatically extracts from the four sites the measured temperatures in Nice and stores them. Another robot creates the above graphs from the data, and adds the sine-wave approximation.
The extracted data is available in four files, one file for CNN, one file for RainOrShine, one file for Weather-Underground, and one file for Nice Airport (extracted from METAR). The first column is the date at which the robot has run, the second is the date found on the Web site, and the third column is the temperature in degrees Celcius.
There are occasional errors (impossible temperatures) and missing days, but on the whole the sites seem to be pretty good at updating their page every day.
The URLs aren't very stable, though. E.g., on Dec 1st, 1999, RainOrShine changed the URL of the forecast for Nice. On Oct 4, 2000, CNN did the same. In May 2010, Accuweather (former RainOrShine) changed URLs again. In September 2017, Weather Underground changed, too. why oh why do people do that!?