Question: Please calculate the average temperature of those trips that started at Market at 4th in 2013.
SQL: SELECT AVG(T2.mean_temperature_f) FROM trip AS T1 INNER JOIN weather AS T2 ON T2.zip_code = T1.zip_code WHERE SUBSTR(CAST(T2.date AS TEXT), -4) = '2013' AND T1.start_station_name = 'Market at 4th'