Create a BigQuery table where each record has an ingestion timestamp. Run a scheduled query to delete all the rows with an ingestion timestamp older than 30 days.

Create a BigQuery table partitioned by datetime value of the weather date. Set up partition expiration to 30 days.

Create a BigQuery table partitioned by ingestion time. Set up partition expiration to 30 days.

Create a BigQuery table with a datetime column for the day the weather data refers to. Run a scheduled query to delete rows with a datetime value older than 30 days.