Question: Which cities have higher temperature in Feb than in Jun or have once served as host cities?
SQL: SELECT T1.city FROM city AS T1 JOIN temperature AS T2 ON T1.city_id  =  T2.city_id WHERE T2.Feb  >  T2.Jun UNION SELECT T3.city FROM city AS T3 JOIN hosting_city AS T4 ON T3.city_id  =  T4.host_city