The pilot stated that, about 45 minutes before departure, he obtained current weather conditions via an internet website and observed a thunderstorm located about 100 miles west of the departure airport. The pilot subsequently departed about 0630 for the local area flight. About 20 minutes into the flight, he recalled seeing a low cloud bank, with a base of about 1,000 feet above ground level (agl), about 1/4 mile east of the airport. At the same time, he noticed an area of heavy rain from clouds located about 15 miles west of his position. He decided to land as soon as possible due to the deteriorating weather. Instead of making an approach to the airport's single runway (17/35), he decided to land toward the west in an open pasture area that was located on the airport property. Shortly after clearing trees and hangars that were located on the east side of the airport, the weight-shift-control aircraft suddenly lost altitude, from about 20 feet agl, and impacted the ground in an upright attitude. After the impact, the aircraft rolled over onto its left side. The pilot reported that the aircraft did not appear to have any forward velocity when it impacted terrain, as indicated by a lack of damage to the surrounding vegetation. The aircraft sustained substantial damage to the wing and fuselage. He stated that there were no mechanical malfunctions of the aircraft that would have precluded normal operation. Additionally, he reported that the aircraft's operating limitations included a maximum headwind and crosswind component of 21 knots and 11 knots, respectively.Meteorological data collected during the accident investigation indicated that, at the time of the accident, there was a squall line of thunderstorm activity present within a few miles of the accident site. Additionally, the National Weather Service (NWS) Storm Prediction Center had issued a warning for the development of severe thunderstorms. The NWS storm warning called for scattered strong-to-severe thunderstorms associated with the passage of a cold front. Local weather stations indicated that there was a wind shift from the south to the north that was associated with the passage of the frontal boundary. The weather stations also reported wind gusts reaching 24 knots. A review of weather radar imagery indicated that, at the time of the pilot's preflight weather check, there was a line of thunderstorms located about 40 miles northwest of the departure airport. The same line of thunderstorms was within a few miles of the airport at the time of the accident and moved through the area almost immediately thereafter.