The pilot stated that the purpose of the flight was to take the 11 passengers on a hot-air balloon sightseeing tour. The pilot reviewed the weather forecast for the day which disclosed that wind speeds would be less than 8 mph. The morning departure occurred in calm wind conditions and the pilot maneuvered the balloon for about 30 to 40 minutes before he noticed the wind was becoming stronger. As he descended to land, he noted that the wind was reaching 15 to 20 mph. In an effort to make a quick stop, he attempted to activate the rapid deflation valve, which was slower than he expected. The balloon subsequently collided with a tree which resulted in substantial damage to the basket.