The Search Bar on your Homepage is pre-populated based on your IP Address or the last known search on that computer.
Based on IP
Pre-population based on IP Address means the pre-populated location may not be the city you are in. For example, you could be in Seattle WA, but the pre-populated location may be Tukwila WA which is about 25 minutes south of Seattle.
Based on Last Search
If you search for a location from the Search Bar on your Homepage, then return to your Homepage you see that the pre-populated location changes to the location you searched for. Each time you do a new search the pre-populated location will update to the most recent search location.