=Cold Waves Tempered by Great Lakes.= The severity of cold waves is markedly modified by the Great Lakes, especially in the fall and the first part of winter, before much of the water surface is covered with ice and snow. Not only is the number of cold waves much less at stations of the Lakes than at near-by places in the interior, but there is a marked variation in the number that occur at the Lake stations, depending upon which side of the lake and how close to the water the station is located. The most striking differences are noted in the Lake Michigan region, the number on the west shore being five or six times as great as on the east side. Milwaukee shows a count of forty-seven as compared with nine at Grand Haven. This lake influence affects the entire Lower Michigan peninsula, but it is not so great in the interior and eastern sections as along the west shore, Grand Haven’s nine standing out against fourteen, fifteen, and twenty-three for Grand Rapids, Detroit, and Port Huron. A similar condition is noted in New York State; Buffalo, Rochester, and Oswego, near the lake shore, had twenty, twenty-seven, and twenty-nine cold waves respectively, while the interior stations of Ithaca, Binghamton, and Syracuse had thirty-eight, forty-five, and fifty-two. =Cold Waves Tempered by the Heat of Cities.= Another reason for the lack of uniformity in the recorded number of cold waves in the various sections of the country is the difference between city and suburban temperatures. Stations located in small villages or in the open land will show a greater number of recorded cold waves than those located in large cities, where the heat stored up by pavements and brick buildings during sunshine each day, and where the heat from thousands of chimneys, and maybe millions of human beings, holds the minimum temperature of night much above that of the free air in the open country. Charles City, where the instruments have open country exposure had sixty-five cold waves, which far exceeds the number recorded at any other station in Iowa. No matter how severe may be the cold wave that appears in the northwest, it will not extend over Wyoming, Colorado, Utah, and any region south of them, unless the center of the High extends well over the Rocky Mountain Divide. Otherwise it will come down the east slope of the mountains and the cold will not cross them.