Work is already under way on the scheme which will help cut launch times and provide enhanced accommodation for the station’s team of 25 boat and shore crew.
The total cost is £1 million and construction is expected to take until October to complete. The 1901 station - a listed building - will be effectively wrapped on two sides by a new extension built partly on land the RNLI has bought to the west of the existing building.
Minehead RNLI chairman Richard Newton said the project was receiving a steady stream of local donations.
"From the very young - like the nursery group - to pensioners’ groups, we are drawing support from right across the community," he said.
"It’s hugely gratifying to know so many people want to support our crew in their life-saving work."