Air pressure at the lower boundary of the atmosphere nearest the surface. In the central North Pacific, trade winds blow in from the northeast from a region of high pressure known as the Pacific Anticyclone, or Pacific High. Its location is typically well north and east of Hawaiʻi, though it migrates north and south with the sun. In summer, it reaches its northern-most position and brings prevalent trade winds across Hawaiʻi during May-September. In winter, however, the heart of the trade winds moves south of Hawaiʻi. Nevertheless, the trades still blow across the islands much of the time, though with a frequency that has decreased to 50-80% in terms of average monthly values.