Over the past year, an ongoing and severe drought has parched most of Mexico, draining reservoirs and leaving parts of the country grappling with an acute water crisis. Since mid-March, scorching temperatures have led to at least 26 heat-related deaths, according to the nation’s health ministry. The double-whammy of weather phenomena, scientists have warned, is aggravated by climate change — which alters usual weather patterns and results in longer and hotter periods with less rain.