Pacific ocean temperatures, tropical rainfall and vertical motion patterns greatly affect the distribution of atmospheric heating across the tropical and subtropical Pacific. Normally, the strongest heating and warmest air temperatures coincide with the warmest ocean waters and heaviest rainfall. This atmospheric heating helps determine the overall north-south temperature differences in both hemispheres, which significantly affects the strength and location of the jet streams over both the North and South Pacific. This influence on the jet streams tends to be most pronounced during the respective hemisphere's winter season, when both the location and eastward extent of the jets (to just east of the date line) exhibit a strong relationship to the pattern of tropical heating. These jet streams are then a major factor controlling the winter weather patterns and storm tracks in the middle latitudes over both North and South America.