Hi Irc! At the end of the day, the value of the weather data you choose is in how closely it matches the weather conditions at your site. In many cases data will be available for your site's location, but when it is necessary to select a nearby location instead, you will want to select one in which similar weather conditions obtain. Usually this will be the closest available weather site, but this may not always be the case. If you're ever unsure, compare weather history between sites to see what the closest match to your site is.