CLIMATE. 
13 
4 - CLIMATE. 
The climate of the Adirondack Wilderness varies greatly with the 
season. Snow covers the ground from some time in November till 
the middle or latter part of April, and in mid-winter averages over 
four feet in depth on the level. During this period the mercury 
often falls below — - 25 ° Fahr. ( — 32 0 C.), and more than once it 
has been frozen ( — 40° F. and C.) In summer the days are warm 
and the nights cool. Owing to the altitude of the region its mean 
annual temperature falls considerably below that of the surrounding 
country. Guyot says : “ On an average an increase of three hundred 
and thirty feet of altitude diminishes the temperature one degree 
Fahrenheit; hence the rate of diminution is about three degrees to 
every thousand feet.” Therefore the temperature at the summit of 
Mt. Marcy should average sixteen degrees Fahrenheit below that of 
tide-level in the same latitude. Mr. Verplanck Colvin found, from 
observations made at three sets of localities, in 1876, that the mean 
decrease in temperature per each thousand feet increase in altitude, 
in this region was 2.93 0 Fahr. in August, 4.1 1° F. in September, and 
4 . 52 ° F. in November.* On this basis the mean temperature of that 
portion of the Adirondacks having an altitude of four thousand feet 
(1,219.20 metres) would average below that of New York city during 
the same time, 11.72 0 F. in August, 16.44° F. in September, and 
18.08° F. in November, il in the same latitude. 
There are probably few places on this continent that are subject to 
greater or more sudden changes of temperature than this area. Vari- 
ations of forty, fifty, and sixty degrees Fahrenheit, during the twenty- 
four hours, are by no means uncommon; and I have seen the mercury 
fall over seventy degrees Fahrenheit in fifteen hours in winter. My 
journal records arise of 42° in six hours, of 32° in five hours, and of 
12° in one hour; a fall of 38° in thirteen hours, and one of 20° in four 
hours. These great and rapid changes usually occur in winter — dur- 
* Report of Adirondack Survey, Verplanck Colvin, Superintendent, 1880, pp. 324-6, 
