Nosebleed in too hot weather may be caused by dryness of nasal mucosa, vascular dilatation, blood system diseases, tumor and other factors. 1. Nasal mucous membrane dryness: when the weather is hot, the water of nasal mucous membrane evaporates faster, which can lead to nasal mucous membrane too dry, and the mucous membrane blood vessels can be ruptured and lead to nasal bleeding. 2. Vasodilatation: the expansion of arterial and venous blood vessels in the nasal cavity is more obvious in hot weather, and the expansion of blood vessel filling leads to the increase of the brittleness of blood vessel wall, which is also prone to the occurrence of nosebleed. 3. Blood system diseases: Combined with abnormal coagulation function, thrombocytopenia and other blood system diseases, the probability of nosebleed can be increased when the weather is hot. 4. Tumors: when tumors and other occupying lesions occur in the nasal cavity, they can lead to local mucosal blood vessels being invaded, thus resulting in nosebleeds. If you have nosebleed when it is too hot, you can consult a doctor in time and take appropriate treatment under the guidance of a specialized doctor.