Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_78612 ( "Week" real, "Date" text, "Opponent" text, "Result" text, "Attendance" real )

### Question ###
What is the attendance for the game against the Kansas City Chiefs earlier than week 13?

### Accurate SQL ###

SELECT AVG("Attendance") FROM table_78612 WHERE "Opponent" = 'kansas city chiefs' AND "Week" < '13'