The overflowing river waters inundated the Ban Tiew community near the fresh market in Muang municipality as well as the Talad Muang Mai, Kok Moongchie, and Ban Mai communities.
Residents of the communities had to rush with their valuables to higher ground.
The water level was over a metre high.
Ten schools in the municipality and other tambons were closed on Friday.
The Kood Pong Park and the Loei Stadium as well as main roads were also inundated. The bridge linking the Ban Tiew community to the community across the river was damaged.
The provincial administration said the heavy downpour has continued since Tuesday evening. The local meteorological office said it was the heaviest rainfall the province had seen in 85 years.