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A temperature of 33 degrees is enough and the risk of having a stroke increases. And it increases immediately: within minutes. A Chinese study published on Jama Network Open conducted on over 82,000 patients with acute ischemic stroke (the most frequent form of stroke, with 85% of total cases) has demonstrated that exposing oneself to temperatures above approximately 33 degrees (already at 33.3° C) leads to a increased risk of acute cerebrovascular episodes already in the first hour of exposure (i.e. at zero hours), and that one remains at risk for 10 hours.