Headache in the sun, may be related to cerebral vascular expansion, may also be due to migraine, heat stroke and other reasons. 1. Cerebral vasodilatation: when the sun is shining, the head is exposed to high temperatures, which can easily cause cerebral vasodilatation, resulting in a relative lack of blood supply to the brain, which may cause headaches, and may be accompanied by dizziness, weakness and other manifestations. 2. Migraine: If there is a history of migraine, the sun, by the influence of high temperature, is likely to induce migraine attacks, may cause headaches, may also be accompanied by dizziness, nausea and other symptoms, 3. Heat stroke: When the body is unable to adapt to and tolerate the high temperature and windlessness of the environment, the body produces more heat than it emits, resulting in heat accumulation and increase in body temperature, and then heat stroke occurs. Patients may experience headache, dizziness, thirst, excessive sweating and other symptoms. Headache in the sun, may also be caused by other reasons, if the headache symptoms continue to be unable to relieve, it is recommended to seek medical attention as soon as possible to diagnose the cause, to give targeted treatment.