To determine if a table exists, it’s best to go against the sys.objects view by querying the object_id using the fully qualified name of the table. The additional ‘type’ field in the where clause ensures that the table that is about to be dropped is a User table and not a system table.
DROP TABLE [dbo].[DumpMe]
To drop a temp table you need to look in the tempdb database for it’s existence.
DROP TABLE #Temp
Once again, I would highly recommend double checking your code prior to issuing these statements.