SELECT station_id FROM weekly_weather WHERE "low_temperature" <= 50 UNION SELECT station_id FROM route WHERE "station_id" = 2 AND "train_id" > 5 <table_name> : weekly_weather col : station_id | day_of_week | high_temperature | low_temperature | precipitation | wind_speed_mph row 1 : 1 | Monday | 59 | 54 | 90.0 | 13 row 2 : 1 | Tuesday | 66 | 55 | 20.0 | 12 row 3 : 1 | Wednesday | 60 | 52 | 10.0 | 14 row 4 : 1 | Thursday | 55 | 50 | 30.0 | 13 row 5 : 1 | Friday | 55 | 52 | 50.0 | 17 row 6 : 1 | Saturday | 55 | 52 | 50.0 | 14 row 7 : 1 | Sunday | 54 | 52 | 50.0 | 12 row 8 : 2 | Monday | 58 | 54 | 60.0 | 20 row 9 : 2 | Tuesday | 57 | 54 | 80.0 | 22 row 10 : 2 | Wednesday | 59 | 55 | 90.0 | 23 row 11 : 2 | Thursday | 59 | 56 | 70.0 | 24 row 12 : 3 | Monday | 49 | 46 | 30.0 | 10 row 13 : 3 | Tuesday | 50 | 49 | 50.0 | 9 row 14 : 3 | Wednesday | 55 | 54 | 60.0 | 8 row 15 : 4 | Monday | 58 | 54 | 70.0 | 7 row 16 : 10 | Tuesday | 59 | 52 | 90.0 | 22 <table_name> : route col : train_id | station_id row 1 : 1 | 1 row 2 : 1 | 2 row 3 : 1 | 3 row 4 : 2 | 1 row 5 : 2 | 3 row 6 : 2 | 7 row 7 : 3 | 4 row 8 : 4 | 6 row 9 : 4 | 2 row 10 : 5 | 1 row 11 : 6 | 5 row 12 : 7 | 4 row 13 : 7 | 5 row 14 : 7 | 8 row 15 : 8 | 8 row 16 : 9 | 7 row 17 : 9 | 8 row 18 : 10 | 9
col : station_id row 1 : 1 row 2 : 3