A Tempest Looms

'A Tempest Looms' is a mission found in New Austin at the beginning of the game. It is undertaken while Marston is at Bonny McFarlene's ranch

According to IGN, the mission is, "brilliantly dramatic", and "we're only half-joking when we say this could be RDR's Four Leaf Clover"

Mission Overview
In 'A Tempest Looms', Marston must herd cows back to the ranch while a massive thunderstorm approaches.