CLIMATOLOGY OF NEBRASKA. 29 



Mean Temperature oe the Whole Year. 



The mean temperature of the whole year in Nebraska, not- 

 withstanding the extreme cold of winter, is remarkably high. 

 The mean yearly isotherm of55°, for example, which passes 

 through Washington, D. C, Cincinnati, and southern Iowa, 

 strikes the Missouri River a little south of Nebraska City, 

 and then moving a little north of west crosses the Platte 

 near Columbus, and thence in a northwesterly direction across 

 the State. This mean annual isotherm therefore embraces 

 over one-half of the State. The mean yearly isotherm of 52^° 

 which passes through Pittsburgh, Pennsylvania, crossing the centre 

 of Iowa diagonally, strikes the Missouri River above Sioux City, 

 thence following the river for some distance takes in the whole of 

 Nebraska not included in the yearly isotherm of 55 . The yearly 

 isotherm of 57J^° passes south of Nebraska. A portion of south- 

 ern and southwestern Nebraska is therefore included between the 

 yearly isotherms of 575^° and 55 and the balance between ^° 

 and 52^°. 



Extremes of Temperature. 



In Dr. Childs' record (Table) ofnineteen years the mercury 

 rose to ioo° F., and upwards, twenty-nine times, or on an av- 

 erage a little more than a day and a half a year. The hot- 

 test year was that of 1874, when in July and August, the 

 thermometer rose to 100 and upwards on twelve different 

 davs. On July 13th it rose to 113 , it being the hottest day accord- 

 ing to Dr. Childs' record, in nineteen years. 



In table C, it will be seen how many days during the time from 

 1 86 1 to 1876, the mercury fell below zero. It will also be seen from 

 this record that while the mean temperature of Nebraska is high 

 for a region in these latitudes, its extremes are great. And yet no 

 acute suffering or other ill consequences flow from it. As we will 

 hereafter see, the heat of summer is modified by the breezes that 

 fan the land. On the other hand, the severe cold of the extreme 

 days of winter are made endurable by the dryness of the atmos- 

 phere. The dryness is so great and potent that the cold is not felt 

 here more when the thermometer marks twenty degrees below 

 than it is in Pennsylvania when only at zero. The reason of this 

 is well understood. It is moisture that intensifies the sensation of 

 chilliness. Every one knows the meaning of a drizzly, chilly day. 

 It is because the atmosphere in the east is more filled with moisture 



