searching and storing from HTML pages

Question

I want to download an HTML page and search for and store for specific data, but I can't think of how to search for and grab the data.

The application I have in mind is for reseaching weather data for my location, that is updated every 10 minutes. I would grab the data every hour, store it, and then process it in any number of ways eg monitor pressure for sudden changes, or monitor dew point etc.