Several days and nights of warm temperatures allowed much of an unseasonably high late-season snowpack to melt. The resultant water caused flooding along the Little Wind River and Middle Fork of the Popo Agie River. The towns of Lander and Hudson and agricultural areas along the rivers were hardest hit by the flood waters.

Flood in FREMONT, WYOMING
From 04-JUN-10 22:00:00 to 13-JUN-10 20:00:00 (MST-7)
Location: SINKS CANYON SP
Flood cause: Heavy Rain / Snow Melt
Property damage: 12.00M
Crop damage: 0.00K
Reported by: Emergency Manager

Heavy snow and cool temperatures in May allowed snowpack to remain at unseasonably high levels across the southern end of the Wind River Range. With over 100 years of weather records, the month of May 2010 ranked as the third coldest at Riverton and tied as the fifth coldest at Lander, both neighboring basin towns. The first warm stretch of the early summer season came on June 2, 3, and 4, as basin temperatures finally climbed into the 70s. In turn, the large snowpack begin a rapid melt that quickly inundated area rivers and streams.
The Middle Fork of the Popo Agie River experienced a rapid rise on Friday afternoon, June 4. The rising waters caused flooding by late evening in the Popo Agie Ranch Estates subdivision south of Lander. Neighbors assisted each other with sandbagging efforts as the water rose through the evening hours. By mid-morning Saturday, June 5, water was causing flooding downstream to the town of Hudson at the confluence of the Middle Fork and Little Popo Agie rivers. Homeowners on the town's west side and farmers and ranchers upstream of Hudson frantically worked to sandbag areas that were not yet inundated by the rapidly rising waters.
Snow continued to melt through the weekend and into Monday, June 7, further exacerbating the flooding. The Mortimore Lane bridge south of Lander was effectively rendered unusable by late morning, June 7. At least five other private bridges in the area were destroyed, as well. Campgrounds in Sinks Canyon State Park were flooded as were Fremont and Third streets in Lander. The Wyoming governor declared all of Fremont County a disaster area on June 7. The Middle Fork of the Popo Agie River near Lander finally crested at 7.50 feet around 2230MST on June 7. This was short of the record of 7.69 feet achieved in June 1963.
As water begin to recede along the Middle Fork, the attention shifted to areas downstream along the Little Wind River. Water levels near the confluence of the Popo Agie and Little Wind rivers around Arapahoe caused 14 homes and several roads to be damaged in that area. A private campground and the historic 1838 Rendezvous site near Riverton were flooded. Farther west along the Little Wind River, the safety of the 17 Mile Road bridge was compromised as the water rose to a record crest. Around 0045MST Wednesday, June 9, the Little Wind River topped out at 11.91 feet, completely shattering the previous record crest of 10.9 feet set in June 1963.
In the end, over 32 square miles of land was impacted by the flood waters, including 38 homes. None of the homes were destroyed. The Wyoming National Guard deployed 400 soldiers to assist in the flood fighting efforts at the peak of the event and over 400,000 sandbags were used. The president declared the county a disaster area on July 14. Public infrastructure damage totaled at least $7.6 million and flood response efforts were estimated at $1.6 million.