HSBC and Santander customers can take repayment holidays and overdraft extensions.
Nationwide customers meanwhile can utilise temporary overdrafts or increased overdraft limits to cover emergency expenses.
The banks are committing people to affected areas, as loss adjusters from HSBC have been deployed in worst-hit areas of Somerset and the Thames Valley to ensure claims can be processed quickly.
Antonio Simoes, head of HSBC in the UK, said: “We understand the huge strain the floods are placing on our business and personal customers in affected areas and we want to make sure we are providing the support that they need now and in the future.
“We recognise that the consequences of the floods will be long lasting and we will continue to provide the financial support and flexibility our customers need.”
Nationwide customers can call emergency support teams, while HSBC are contacting some customers directly by locating properties at risk using the latest mapping technologies.
HSBC are waiving or reducing arrangement fees on loans, in addition to offering fast-track credit acceptance and loan and overdraft extensions, while Nationwide are taking into account that customers may not have all the relevant documentation to hand, and are instead offering alternative ways to securely identify and assist members.