If you want to explore when it's quieter, go in February. You could find some fantastic deals on hotels with parking in Jombang around then. The warmest conditions are in September, with temperatures ranging from 72ºF (22ºC) to 95ºF (35ºC). It's often coolest in February, averaging between 72ºF (22ºC) and 86ºF (30ºC).