Colorado Climatology 
9 
from October 1st to May 1st, the total precipitation was only 
0.82 inches, .44 of which fell in one storm in November, but 
fortunately this period was followed by a wet May, 5.83 inches, 
which was followed by favorable rainfall, permitting good 
crops to be secured. 
Absence of precipitation does not always mean drouth, 
especially when the soil is moist and evaporation is retarded 
by cloudiness and unfavorable wind conditions. Therefore, 
the maximum period without rainfall as a measure of the in¬ 
tensity of drouth must take into calculation the previous period 
and these other conditions. Then again the maximum period 
without rainfall often, in fact usually, occurs during the non¬ 
growing season, the autumn and early winter months having 
little or no effect on crops except that we need all the snow we 
can get on the high mountains for next season’s supply. There 
is quite a wide range between the amount of precipitation in 
the wettest and driest years. For the wetter years the differ¬ 
ence in amount may be two or three times the amount of the 
drier years. The snowfall for the winter months in Colorado 
is small, the average for November and December being the 
least in the year. However, on the crest of the range and on 
the high mountains, the snowfall is heavier and is stored there, 
especially in large drifts in the timber and gulches and north 
hillsides, for use in irrigation the following season. 
STREAMS CARRY MOST IRRIGATION WATER IN MAY AND JUNE 
While many of the streams of the State have a good flow 
during May and June, they fall short during the months of 
July and August, at a time when some of our most valuable 
crops are in need of water. During times when the flow is 
plentiful a supply of water that would otherwise go to waste 
and help increase the damage due to floods lower down, can 
be impounded in our reservoirs and put to a beneficial use to 
water our best paying crops later in the season. This condi¬ 
tion arises almost every year, because our best months for rain 
are April, May and June, which is the time the melting snows 
cause the rivers and streams to be in a flood stage, and as the 
rains on the plains supply sufficient moisture for growing 
crops, the water then flowing in the streams is available for 
the reservoirs. 
The storms during the summer months are local in char¬ 
acter and vary considerably in the amount, from nothing to 
an inch or more, and in their frequency, sometimes one or more 
every day for ten days or two weeks, and then again they are 
