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The history of Columbia County, Wisconsin, containing an account of its settlement, growth, development and resources; an extensive and minute sketch of its cities, towns and villages--their improvements, industries, manufactories, churches, schools and societies; its war record, biographical sketches, portraits of prominent men and early settlers; the whole preceded by a history of Wisconsin, statistics of the state, and an abstract of its laws and constitution and of the constitution of the United States
(1880)

Oldenhage, H. H.
Climatology of Wisconsin,   pp. [121]-128 PDF (3.9 MB)


Page 124


24HISTOIRY OF WISCONSIN.
state, and the lowest 64Q at Bayfield, Lake Superior.  During the months
of June, July and
August, the thermometer often rises as higk as 9oQ, seldom to iool. In 1874
the mercury reached
this high point twice at LaCrosse, and three times at Dubuque, Iowa. There
are.usually two or
three of these "heated terms " during the summer, terminated by
abrupt changes of temperature.
      The isotherm of 7o0 (an isotherm being a line connecting places.having
the same mean tem-
 perature) enters this state from the west. in the northern part of Grant
county, touches Madison, takes
 a southerly direction through Walworth county, passes through southern Michigan,
Cleveland, and
 Pittsburg, reaching the Atlantic ocean a little north of New York city.
From this it is seen that
 southern Wisconsin, southern and central Michigan, northern Ohio, central
Pennsylvania, and
 southern New York have nearly the same summer temperature.  Northwestward
this line runs
 through southern Minnesota and along the Missouri to-the foot of the mountains.
Eastern Ore-
 gon, at 470 3o0 north latitude, has the same average summer temperature;
the line then returns
 and touches the Pacific coast at San Diego.
     The remarkable manner in which so large a body of water as Lake Michigan
modifies the
 temperature has been carefully determined, so far as it relates to Wisconsin,
by the late Dr. Lap-
 ham, of Milwaukee.  It is seen by the map that the average summer temperature
of Racine is
 the same as that of St. Paul. The weather map for July, 1875, in the signal
service report for
 1876, shows that the mean temperature for July was the same in Rock county,
in the southern
 part of the state, as that of Breckenridge, Minn., north of St. Paul.  The
moderating effect of
 the lake during hot weather is felt in the adjacent region during both day
and night.
     Countries in the higher latitudes having an extreme summer temperature
are usually charac-
 terized by a small amount of rain-fall. The Mississippi valley, however,
is directly exposed in
 spring and summer to the*warm and moist winds from the south, and as these
winds condense
 their moisture by coming in contact with colder upper currents from the
north and west, it has a
 profusion of rain which deprives the climate largely of its continental
features.  As already
 stated, the average amount of rain-fall in Wisconsin is about 30 inches
annually. Of this amount
 about one-eighth is precipitated in winter, three-eighths in summer, and
the rest is equally dis-
 tributed between spring and autumn -.in other words, rain is abundant at
the time of the year
 when it is most needed. In Wisconsin the rainfall is greatest in the southwestern
part of the
 state; the least on and along the shore of Lake Michigan. This shows that
the humidity of the
 air of a given area can be greater, and the rainfall less, than that of
some other.
     In comparison with western Europe, even where the mean temperature is
higher than in the
 Mississippi valley, the most striking fact in the climatic conditions of
the United States is the
 great range of plants of tropical or sub-tropical origin, such as Indian
corn, tobacco, etc.  The
 conditions on which the character of the vegetation depends are temperature
and moisture, and
 the mechanical and chemical composition of the-soil.
     "The basis of this great capacity (the great range of plants) is
the high curve of heat and
 moisture for the summer, and the fact that the measure of heat and of rain
are almost or quite
 tropical for a period in duration from one to five months, in the range
from Quebec to the coast
 of the Gulf." Indian corn attains its full perfection between the summer
isotherms 72Q and 770,
 in Illinois, Iowa, Missouri, and Kansas; but it may be grown up to the line'of
659, which includes
 the whole of Wisconsin. The successful cultivation of this important staple
is due'to the intense
 heat of summer and a virgin soil rich in nitrogen.
     While Milwaukee and central Wisconsin have a mean annual temperature
of 450, that of
 southern Ireland and central England is 500; the line of 72", the average
temperature for July,
runs from Walworth county to St. Paul, while during the same month Ireland
and England have
a mean temperature of onJy 6o0. In Wisconsin the thermometer rises as high
as 9o'q and above,
124


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