cold water

Q: While in the state of janabah, due to cold weather and lack of warm water, can a person offer Salah without ghusl? If not then what is the Shariah ruling?

Q: Some nights I become impure by wet dream and at time of fajr water is so cold, if I take a bath I would fall in cold and fever. Although time is so limited that if I boil water I must miss the salaah. In this circumstance can I just make wudu instead of ghusl and perform fajr?