Le site weather.cod.edu est-il sûr ?

It's just a site with weather data. You probably will have a hard time interpreting a lot of the data here if you're not a meteorology geek and thus aren't familiar with the terminology and what the data means, but I don't see any security issues. It is a website run by the College of DuPage in Illinois, and what that means for your opinion of the site is up to you, since I sure as hell don't know much about the aforementioned college.