In the Southern Hemisphere there is not such a pronounced shifting of the Highs and the Lows from oceans to continents and back again, with change in the seasons, as there is in the Northern Hemisphere, because of the small area of land in comparison with that of water; but in the midst of the southern summer, which occurs in January (Chart 2), Lows are shown over South America, Africa, and Australia. Note how the winds blow out of all the Highs and into all the Lows. Also observe that the winds generally blow from about latitude 30° north and south towards the equator, due to the great heat of the tropics, which causes the air to rise and in the high levels to flow northward and southward, settling down to the earth again through the belts of high pressure that irregularly encircle the earth at latitudes 30° north and south. In the interior of continents the temperature falls lower at night and rises higher during the day, and falls lower in winter and rises higher in summer than on any of their coasts. On the coast of central California, for instance, the ocean is so cool in summer and the winds blow so steadily from it that the thermometer ranges between 55° and 70°, even when there are temperatures of over 100° but a few hundred miles away in the great interior valleys, or on the broad plateaus of the mountains. New York and Boston, in nearly the same latitude, also have their summer temperatures modified by ocean influence, but they are on the east side of a broad continent, where the prevailing westerly winds give to them more the character of a continental climate than one marine; but occasionally the east wind, for a short time, gives to them the modifying influence of the ocean. In the winter the influence of the oceans is to modify the extremes of cold, the same as they do the excessive heat of summer. [Illustration: CHART 12.—AVERAGE MAXIMUM TEMPERATURE FOR JULY (Henry).] Chart 8 (page 129) showing the lowest temperatures ever recorded at Weather Bureau stations, and Chart 12, presenting the average of the highest daily temperatures of July, graphically show, clearer than any text can describe, the influence of continents and oceans on climate. On the Atlantic the average maximum of day varies from 70° on the Maine coast to 85° on the coast of North Carolina; while on the Pacific, where the marine influence is stronger, the average is from 65° on the Washington coast to 80° on the coast of southern California. But near the center of the United States where the continental influence predominates, the average of the highest daily temperatures varies from 85° to 90°. On Chart 8, showing the lowest temperatures, the line of 20° below zero passes through Boston, southwest to Chattanooga, west to Flagstaff, Arizona, and then irregularly north to Seattle, showing the influence of both oceans in carrying the line northward. [Illustration: CHART 13.—OCEAN CURRENTS.]