Nose bleed or Epistaxis is not life threatening. There are many reasons for Epistaxis. But since you have mentioned your city so I think for you it is extreme change of temperature. It's a myth that only extreme hot temperature causes nose bleed, staying at cold air conditioned room can also cause nose to dry and bleed too. Therefore it is very common in summers. Both extreme cold and hot temperature can cause nose bleeding. The vessels in nasal septum are very sensitive they react to the changes in temperature. Other causes are nasal infections, nasal trauma, bleeding disorders, alcohol consumption, liver diseases and sinus infections.