Not really. Interest rates are as good in non-ISA accounts, and you are allowed to earn up to £1,000 in interest per year tax-free. With interest rates at under 5%, this means you’d need around £20,000 in cash to be benefiting from the tax sheltered status. £20k is beyond emergency fund territory and this money should be invested instead.

It’s possible you are in an odd situation where you temporarily have large amounts of cash, such as whilst you are waiting for a house purchase to go through. Even then cash ISAs are of limited use, since their contribution limits of £20k per year won’t allow you to quickly shunt all of your house purchase cash into the tax shelter.