Blocking access by remote users for a specific time period

I have several web apps that access our Postgresql database that I'd like
to lock out of the database for about an hour during a weekly maintenance
interval. (There are some internal users that do not get locked out,
because they're running the maintenance tasks.)

There are no time-of-day access limitation parameters in the pg_hba.conf
file, are there any simple ways to do this?
--
Mike Nolan