The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
A simple to use utility to calculate the distance to a storm based on the time elapsed between the lightning and the thunder.When you see the lightning: hit the 'Lightning' button, then when you hear the thunder: hit the 'Thunder' button. The distance to the storm will be shown.