RED SNOW

Red Snow was a British thermonuclear weapon, based on the US W28 design used in the B28 thermonuclear bomb and AGM-28 Hound Dog missile. The US W28 had yields of 70, 350, 1,100 and 1,450 kilotonnes of TNT and while Red Snow yields are still classified, declassified British documents indicate the existence of "kiloton Red Snow" and "megaton Red Snow" variants of the weapon, suggesting similar yield... (Wikipedia)