Tehuantepecer, or Tehuano wind, is a violent mountain-gap wind traveling through Chivela Pass, most common between October and February, with a summer maximum in July. It originates from eastern Mexico and the Bay of Campeche as a post-frontal northerly wind, accelerated southward by cold air damming, which crosses the isthmus and blows through the gap between the Mexican and Guatemalan mountains.