Write SQL query to solve given problem: For the home weather station of store no.15, what was the dew point on 2012/2/18?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T1.dewpoint FROM weather AS T1 INNER JOIN relation AS T2 ON T1.station_nbr = T2.station_nbr WHERE T2.store_nbr = 15 AND T1.`date` = '2012-02-18'