xt7mw6694n3d https://exploreuk.uky.edu/dips/xt7mw6694n3d/data/mets.xml   Kentucky Agricultural Experiment Station. 1975 journals 221 English Lexington : Agricultural Experiment Station, University of Kentucky Contact the Special Collections Research Center for information regarding rights and use of this collection. Kentucky Agricultural Experiment Station Progress report (Kentucky Agricultural Experiment Station) n.221 text Progress report (Kentucky Agricultural Experiment Station) n.221 1975 2014 true xt7mw6694n3d section xt7mw6694n3d f EI¤II¥H\”I’E IEIF I&EN‘ I ’IilEI&
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UNIVERSITY OF KENT A ` Ir   '`‘‘“  " ""”·*"*’“°»=’~  
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D8 CULTURE AGRICULTURAL EXPERIIVIENT STATION
A partment of Agronomy . Lexington

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Kentucky climatic divisions. —

 CONTENTS
Page
Introduction ....................... 5
Weather Systems Affecting Kentucky .............. 5
  Precipitation ....................... 8 y
Temperature ....................... 9
_ Frost and Freezes ..................... 13
Wind .......................... 14
Relative Humidity ..................... 15
Cloudiness ........................ 16
Solar Radiation ...................... 16
Evaporation ....................... 17 ,
Soil Temperatures ..................... 18
Drought ......................... 20
Severe Storms ....................... 20
Floods ......................... 22
. Sources of Climatological Data ................ 23
Appendix I—Monthly Temperature Means ............ 25
Appendix II—Monthly Precipitation Normals ........... 26
- Appendix IH—Loca1 Climatological Summaries for
28 Locations in Kentucky ............ 28
3

 b
ACKNOWLEDGEMENTS
The author acknowledges the support of the Division of Water in the
Kentucky Department for Natural Resources and Environmental Protection
which maintains the long record ol our state’s weather observations used in
this report. Mrs. Catherine DeBoer, once again, was invaluable for her help
in evaluating the data and typing the manuscript.
»l»

 By ferry D. Hill*
Kentucky has a number of natural resources, In each case, the daily observations are made E
but among the most important is an extremely in a spirit of service to an individual’s community
agreeable climate. If one were to design a climate and fellow man. There are many examples of
suitable for a wide-range of activities, it would exemplary service among this group, such as Mr.
likely be similar to that which dominates the and Mrs. Cecil Lovell who have been taking daily
Bluegrass state. Precipitation is ample without a weather observations at their home in Greenville
pronounced dry season, and temperatures are since 1916. Mr. Frank Street, of llenderson, has
moderate during both winter and summer. There is the enviable record of maintaining a weather
a minimum of snowfall to disrupt transporation station on his farm with an unbroken string of
$5 and commerce during the winter. Among the many observations dating back to the day he started on
J systems used to classify the climates of the world, Sept. 1, 1936. It 1S to all of these devoted
the word temperate is most commonly found as a volunteers that this study of Kentucky’s climate is
i description of the kind which Kentucky enjoys. dedicated.
The ideal nature of Kentucky climate is
apparent in its agriculture where production is WEATHER SYSTEMS AFFECTING KENTUCKY
seldom seriously limited by weather factors. The
evenly-distributed rainfall keeps an ample supply Almost all of the United States comes under
of water in most rivers year-round and allows the influence ofhigh andlowpressure centers which
major streams to be impounded to form large lakes move across the country bringing irregular and `
providing a source of recreation to millions. sometimes dramatic changes in the weather. These
While the long-term average weather condi- pressure centers are responsible for distinct types
tions may seem ideal, there are ranges within which of weather as they move generally from west to
it usually varies and extremes which may be east. The low pressure centers have rain and
reached. In any type of long—range planning it is cloudiness associated with them, while high pres-
` useful to know the average conditions for a sure centers are usually accompanied by clear skies
particular location as well as the extremes. For this and fair weather. These pressure systems have
_ reason, a study has been made of the various favored regions where they tend to form and
weather factors over a long period of time to preferred routes which they follow as they move
determine the climate. across the country. Kentucky is one of the states
To determine the average weather conditions, which finds itself in the path of frequent passages
it is necessary to have continuous weather observa- of these weather-makers, causing considerable
tions from many locations. Most climatologists feel variability in the day-to—day weather. ‘
that a minimum of 30 years of observations is During the winter the pressure centers move
required to properly document the long-term along paths which cross much of the continental
average. In Kentucky, numerous dedicated volun- United States bringing changeable weather to most
teer weather observers have taken daily weather states. In the summer the paths are drawn north-
observations of temperature and precipitation for ward over the Great l.akes and (Zanada so there are
many years. Many of these observers are private less frequent changes in Kentueky’s weatlier and
citizens such as farmers, businessmen, and house- more prolonged periods of warm temperatures
wives, while others are the personnel of radio Often, during the summer, a high pressure center
stations, educational institutions, utility compa- will become stationary along the eastern coast of
nies, or some other organization which rotates the the United States. Southerly winds on the western
duty among its employees. side of the high will bring moisture from the Gulf
*Aclvisory Agricultural Nleteorologist, National O: eanie and Atinosplierit; Atlrniiiistratioir, National \\`<·atl1<·r St rvir <·. l.¤·>;in¢.{ton. K5.
5

 WINTER SUMMER
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Fig. 1.—Prcfcrrcd tracks 0f low prcssurc ccntcrs.
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Fig. 2. · Prcfcrrcd tracks of high prcssurc ccntcrs.
6

                  
       
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 of Mexico northward up the Mississippi Valley into annual total ever reported from an official ob-
Kentucky where showers tend to develop during serving station was 79.68 inches at Russellville
the afternoon when daytime heating causes air to during 1950. »
rise. This weather pattern may persist for several The mountains of eastern Kentucky form a A `
days until a shift in the wind brings drier air from a barrier to the eastward movement of air which
continental region. might normally be expected to increase precipita- .
tion amounts owing to the additional lifting as the
air is forced over them, but this is not apparent in
PRECIPITATION the weather observations from that region. Average
annual rainfall in that section of the state is about
The regular movement of low pressure 43 to 45 inches. One possible reason for the lack of
systems across Kentucky during the winter brings widespread observations of increased rainfall over
frequent precipitation to all sections. During the the mountains is that the prevailing winds are
summer, the showers which develop bring generally southwesterly nearly all year, causing the air to
ample rainfall from june through August. If a dry move along the prominent ridge lines rather than .
season could be said to exist in Kentucky it would being lifted over them.
be during September and October when the high The frequent passage of low pressure centers,
pressure dominating the southeastern United States especially Clufiflg tl1€ cooler $@3-SOD is 2lpp&Y€¤“K in
extends into the Mississippi Valley and blocks out the data showing the number of days with 0.01 ·
some of the moisture available from the Gulf of inch or more of precipitation each month. On the
Mexico. Average rainfall totals for October are 2 to average, at any particular location there will be
3 inches, making it normally the driest month of Zibmlt 21 dozen d€iY$ with precipitation €€i€h month
the year. from December through May. Summer showers at
Greatest monthly rainfall occurs during March any location are somewhat less frequent but can be
when amounts of 4 to 5 inches are normally expected to occur on about 7 or 8 days each
expected. During the remainder of the months, month during August, September, and October.
except October, rainfall averages from 3 to about Snowfall is limited in many sections of
4.5 inches. On rare occasions, rainfall observers Kentucky and ranges from about 5 to 10 inches a
have reported an entire month with less than a year in southwestern Kentucky to nearly 25 inches _
measurable amount of precipitation. The greatest in some of the northeastern sections and 40 inches
monthly total was 22.97 inches reported at at higher locations in the southeast. Usually, less
liarliugton in _]anuary 1937. Average monthly than 5% of Kentucky’s annual precipitation total is
precipitation for each of the state`s four climatic received in the form of snow. Extremely heavy
divisions (see inside of front cover) is shown in snowstorms have occurred in the state with
Table 1. Averages for the period 1941-70 at 81 accumulations in excess of 12 inches during a
locations in the state are included in Appendix ll. single day. On March 9, 1960 more than 18 inches
Total annual precipitation averages about 45 of snow fell on Bowling Green in a single day. For
inches. The range is from about 39 inches along the that entire month, Cumby;-land ygcgrdgd 46%
Ohio River in extreme northeastern Kentucky to inches of snow. Generally, the heaviest snowstorms
50 inches in south central Kentucky. The greatest occur during March because the air has become
Table 1.—.·\verage Monthly Precipitation (inches),
(Zlirnatic Month
Division jan. l·`eb. Mar. Apr. May june july Aug. Sep. Oct. Nov. Dec. Annual
Western 4.23 3.81 5.09 4.23 4.43 3.95 3.79 3.33 3.19 2.58 3.85 3.90 46.38
tTeutr.tl 4.16 3.89 5.08 4.19 4.35 4.42 4.39 3.45 3.04 2.47 3.74 3.92 47.10
lilueurass 3.79 3.40 4.74 3.97 4.11 4.19 4.66 3.43 2.95 2.22 3.39 3.35 44.20
liastern 4.02 3.86 4.67 3.89 3.93 4.19 4.97 3.68 3.13 2.40 3.45 3.77 45.97
8

 40    `Rm  _ _
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_{lI;;L°“"‘" GMS     mi .  L[;_ t·n;»L__i'L;·_¤··   ._., ,.,&j'Mi' .,EL,· ` higher elevations.) .
Fig. 6.~Mean annual snowfall (inches).
somewhat warmer than in january and can hold Tl5MPERA'l`URI·]
more moisture. Brief periods of warm weather
which often develop even during mid-winter cause Kentucky has a large annual temperature
any snow accumulation to melt rapidly. The total cycle typical of a mid—continent climate at this
number of days when snow covers the ground to a latitude. january is normally the coldest month of
depth of one inch or more at any particular point the year, while _luly is the warmest. The difference
averages only 10 days a year in western Kentucky in mean temperature between these 2 months is
and 25 days in the east. about 40l·` degrees. The mean annual temperature
9

 in Kentucky ranges from about 58°F in the south- raphy tO ereate an unusual pattern Of the average
west to 54°F in the northeast. Monthly and annual amrmal temperature
mean temperatures for the period 1941-70 are Normally, temperatures would be expeeted te
shown in Appendix I for 34locations in Kentucky. be warmer in the southern portions of the state ·.
The coldest temperature usually experienced and cooler in the north. However, strong southerly
in winter is around 0°F or a few degrees below. winds, especially in the summer, are more pro-
The extremes range down into the -20s, though, at nounced across western Kentucky and tend to
many locations in the state. The coldest ever bring warm air from lower latitudes into that
observed at an official weather observing station in region much more effectively than into the eastern
Kentucky was -34°F, which gccurred at Bonnie- S€CtiOIlS. This I`€SUltS l1'1 tht? warmest t€IHp€I`3.tUI‘€S `
ville in Hart County on jan. 24, 1963 and also at occurring in the southwest and coolest in the
Cynthiana on _]an. 28, 1963. Generally, the coldest ¤0Tth€¤$t·
temperatures in the state occur in the central and The exact Piillcln of m€¤¤ '¤€mP€Y&'€UT€ P1€Y0SS
northeastem portions but considerable variability th€ mmlntalns of eestem K€¤tU€kY is Still relative-
ig rcpgytcd, Oyying to [hc irrggtllay topogyaphy in   unknown. There 3.1`€ few 1OCEIt1OHS in   region
Kentucky. On clear nights when polar air covers which have long l`€€0YdS of t€mP€l`?1lUT€ 0bS€1`V&· -
the state, cold air has a tendency to drain into the tl0¤$» and lh0$€ &l`€ generally located lll the valleys.
lower elevations where temperatures may some- One of tht? l0¤g€$’¤ records in €5lST€1”H K€I1lUCl·L'·.'L‘—lZ’*   i Ow Aye I '
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50 40 30
60
Fig. 8.—Average number of days a year with maximum temperature 90°F or more.
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