How do I correct this value too long for type character varying(5)?
So first, what's the difference..

SELECT x, length(x)
FROM ( VALUES
  ('Cincinnati'),
  ('San Francisco')
) AS t(x);


Here is the output

       x       | length 
---------------+--------
 Cincinnati    |     10
 San Francisco |     13


So..


San Francisco is three characters longer.
They're both over 5 characters.
That can't be the problem.


And further, if Cincinnati was in a varchar(5), it'd have to get truncated.

So the problem is your cityid. It is varchar(5). you probably want that to be an int anyway -- it'll be more compact and faster. So ALTER the table and fix it.

ALTER TABLE cities
  ALTER COLUMN cityid SET DATA TYPE int
  USING cityid::int;


As a side note... maybe someday PostgreSQL will speak column names in error messages. until then at least it's more verbose than SQL Server.