Build a weather program

Question

Hey Guys. 


I have a project in a c# class where i have to build an app that needs to control the following things: Temp, wind speed, and rain for 10 chosen stations in Denmark. 


The following has to be able to extract from each station.  
-Highest temp on a given day
-Lowest temp on a given day
-Median temp on a given day
-Higest windspeed on a given day 
-Lowest windspeed on a given day
-Median windspeed on a given day
-Highest amount of rain on a given day
-Lowest amount of rain on a given day
-The median of fallen rain on a given day


The "given day" just have to be a random day but the same one for all. 


I'm lost on this one. I don't really know how to start building the app.. Any ideas?
We don't need to use internet based API's and all the data can be "fictional"
Any help would be gratefully received.!!
Thanks ..