Lead thieves have been targeting churches "under the cover of storms", the Diocese of Wells and Bath has said.
Four churches in Somerset have had lead stripped from them in the past week, according to the diocese.
About six tonnes of lead was stolen from St Martin's Church in Kingsbury Episcopi during Storm Dennis.
The diocese said storms covered the noise made by thieves and meant there were fewer people around.
Barbara Moore, the warden at Kingsbury Episcopi, said she was "very upset and angry" thieves had attacked the "beautiful medieval building".
"It was the beginning of Storm Dennis and the water came in and all the cushions and seat coverings were soaking," she said.
"It's one of the most historic and significant buildings in the parish.
"There won't be enough in the insurance to pay for it."
Churches in Meare, Middlezoy and Barrington have also been targeted.
Emma Brown, the church building advisor for the diocese, said at least 20 churches in the county have been hit by lead thieves in the last six months.
"It has a great deal of impact on churches particularly those in rural settings," she said.
"These are small congregations, finances are already quite tight so an impact such as this could cost them £40,000 of funds they simply don't have."