Updating A Table With Data From A Temp Table

I am trying to update a table in one database with data from a temporary table which i created in the tempdb.

I want to update field1 in the table with the tempfield1 from the #temp_table

The code looks something like this:

Use master
UPDATE [dbname].dbo.table
SET [dbname].dbo.table.field1 = [tempdb].dbo.#temp_table.tempfield1
WHERE ( [dbname].dbo.table.field2= [tempdb].dbo.#temp_table.tempfield2
AND [dbname].dbo.table.field3= [tempdb].dbo.#temp_table.tempfield3
AND [dbname].dbo.table.field4= [tempdb].dbo.#temp_table.tempfield4)

I get the following error:
Msg 4104, Level 16, State 1, Line 2
The multi-part identifier "tempdb.dbo.#temp_table.tempfield2" could not be bound.
Msg 4104, Level 16, State 1, Line 2
The multi-part identifier "tempdb.dbo.#temp_table.tempfield3" could not be bound.
Msg 4104, Level 16, State 1, Line 2
The multi-part identifier "tempdb.dbo.#temp_table.tempfield4" could not be bound.

What is wrong?