Sea surface temperature data have shown that the area of highest temperatures of the North Pacific, always in the western tropics, increases in spring and summer by expanding northward. Thirty years of ship-injection temperatures are used here to document the year to year SST fluctuations for a given month and the month to month variations for a given year of the large surface area of the western tropics during the warming seasons. Some of the fluctuations are significantly large and may therefore be real. Thus the previously hypothesized exportation of warm surface water northward out of the western tropics at the end of every summer may deliver variable amounts of oceanic heat to mid- and higher latitudes from one year to another. A possible connection with mid-latitude weather changes on time scales of months to years is briefly stated.