294 Wisconsin Academy of Sciences, Arts and Letters. 
sharp drop, and was attended by much wind, clearing weather 
and a rapid increase of barometric pressure. 
In Plate XIX are shown the normal daily variation of Madi¬ 
son’s January temperature and the temperature changes 
during several other decided cold-waves of recent years. The 
weather map conditions preceding these may he noted in the 
table on page 296. Probably the most severe of the cold- 
waves illustrated is shown by trace (G), February 12-13, 
1905, on account of the low temperature at which it oc¬ 
curred, the thermometer reading —24° at 7 a. m. of the 13th. 
Trace (E) for January 30-31, 1906, is of interest from the 
fact that the cold-wave occurred far to the west of the storm 
center which was in eastern Ontario at 7 a. m. of the 30th. 
Trace (D) followed a storm central in Oklahoma with decidedly 
cold weather in Manitoba; few of our cold-waves occur under 
these weather map conditions. 
A tabulation of all the cold waves at Madison during the 
past 20 years shows that approximately 206 have occurred in 
that period, distributed among the calendar months as follows: 
January, . 69 
February, . 56 
March,. 26 
April,. 4 
Xovember,.24 
December,.27 
While the average annual number is thus about 10, during 
1887 no less than 23 occurred. During this 20 year period 
some remarkable falls in temperature have occurred, as may be 
noted from the following table. 
January 29-30, 1887, —50° in 24 hours; 36° in 10 hours. 
March 12, 1887, —32° in 17 hours. 
April 3, 1887, —33° in 17 hours. 
January 12, 1888, —43° in 24 hours. 
February 4, 1889, —42° in 17 hours. 
Febrauary 21-22, 1889, —44° in 24 hours. 
March 24, 1891, —43° in 17 hours. 
January 21-22, 1895, —39° in 24 hours. 
