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 trip ( id number, duration number, start_date text, start_station_name text, start_station_id number, end_date text, end_station_name text, end_station_id number, bike_id number, subscription_type text, zip_code number )
TABLE: CREATE TABLE status ( station_id number, bikes_available number, docks_available number, time text )
TABLE: CREATE TABLE weather ( date text, max_temperature_f number, mean_temperature_f number, min_temperature_f number, max_dew_point_f number, mean_dew_point_f number, min_dew_point_f number, max_humidity number, mean_humidity number, min_humidity number, max_sea_level_pressure_inches number, mean_sea_level_pressure_inches number, min_sea_level_pressure_inches number, max_visibility_miles number, mean_visibility_miles number, min_visibility_miles number, max_wind_speed_mph number, mean_wind_speed_mph number, max_gust_speed_mph number, precipitation_inches number, cloud_cover number, events text, wind_dir_degrees number, zip_code number )
TABLE: CREATE TABLE station ( id number, name text, lat number, long number, dock_count number, city text, installation_date text )

### Question ###
Find all the zip codes in which the max dew point have never reached 70.

### Accurate SQL ###

SELECT DISTINCT zip_code FROM weather EXCEPT SELECT DISTINCT zip_code FROM weather WHERE max_dew_point_f >= 70