122 C-ireular N0. 19.
the ideal dates about which tl1e actual dates fiuctuate from
. year to year. The average date of last killing frost in spring · '
means that it is the date, determined from the records of past -
years, when chances are even that there .will or will not be a _
killing frost later. The average date of first killing frost in t
fall means that date when chances are even as to whether
a. killing frost will come earlier, or whether tl1e first killing Z
frost will occur later than that date. ` · i
But the farmer should know something more definite and I
practical in regard to his frost risk than is given in the dates . 
whe11 he has. in the long run. only an even chance. ln this
study dates giving the probability of killing frost ranging from ‘
i an even chance to OIIC in twenty were computed for ea.ch stai
tion. The computed dates for a few selected risks. or frt·—
‘ queneies, are summarized in the accompanying tables, explained
fully later.
As a rule. tl1e risk of a destructive frost is not so great —
for farmers in Kentucky as it is for those in many other states. '
particularly in those states further north and in those further
_ south. ln Kentucky, most of tl1e principal crops are usually
planted after tl1e time of average killing frost in spring. and
_ mature or are harvested before the average date of killing i
frost in fall, the period between these dates usually being of
suflieient length for the growing and maturing of most of the
staple crops. Occasionally, however, favorable conditions in  
spring bring about early planting and the consequent risk of  
damage from spring frost.: or, perhaps. unfavorable conditions Q
of weather or soil delay planting, which, in turn. increases
the risk of damage from an early fall frost. ln Kentucky.
killing frosts in spring refer mostly to resulting damage to K
fruits. strawberries and early garden truck, corn and tobaeeo
rarely ever being so early planted; while. in the fall. killing
frosts as t`ar as damage to staple crops is concerned, refer
almost entirely to eorn and tobaeeo. tl1e oecurrenee of a. killing
frost praetieally ending the season for those crops. lt not
infrwptently happens. as was the ease during the past two .
years. that both of these crops are matured and well out ol.
danger before the oeeurrenee ot' the first freezing tempe_ratur<· ' _
or a destructive frost. However. it should be recognized that
the farmer should know and heed the risk· he runs and the
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