I used a few websites to predict the flight path of the balloon. You can use the website below  which will give you a KML google earth file. This takes into the consideration the wind and atmospheric conditions. Try to launch away from any oceans. Since I live in Connecticut, I traveled west for launch.
Also, If your payload lands in the water, be sure to keep everything water tight, and buy electronics that are "waterproof."
If your doing this in any country other than the U.S. make sure you ask permission from a government agency.