EDIT: I should be clear. I would not be writing the code. I'd do the legwork to find someone (and pay them) who is familiar working with OSM to process the data, create the dataset, and build a javascript frontend to visualize it. The result would be open source. I would accept no funds whatsoever for this.
I don't have the time to do the project, but that doesn't mean I can find someone who does, and get them paid to do it and make the results freely available.
My ultimate goal is to make a list of cities with less than 10 90 degree days per year. I still don't see a way to do that on wunderground.