Which of these host cities has a lower temperature in March than July.
SELECT T1.city FROM city AS T1 JOIN temperature AS T2 ON T1.city_id   =   T2.city_id WHERE T2.Mar  <  T2.Jul INTERSECT SELECT T3.city FROM city AS T3 JOIN hosting_city AS T4 ON T3.city_id   =   T4.host_city
lower temperature in March than July refers to T2.Mar < T2.Jul; host cities are cities that are hosting or have hosted an event, referred to by the join between city and hosting_city tables;