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As part of a continuing effort to remember, celebrate and learn from our amazing weather, the National Weather Service in Louisville has compiled a list of several "Top 10" events for the County Warning Area (CWA).  Here we present the list of the top 10 heat events that have occurred in central Kentucky and southern Indiana.  While many drought or heat wave events have occurred in the CWA we tried to pin point the top ten most memorable.

As is often the case with meteorological extremes, it is difficult to confine over a hundred years of climatology into a list of just 10 events.  This is a particular challenge with something such as broad as heat.  In compiling this list, events were weighed based on the degree in temperature, the length of the event, and the drought factor that occurred.  It should also be noted that for those who are left to pick through the devastation of destroyed crops or even the loss of life due to the heat wave, that event will forever be the most significant.  If you wish to express your feelings about this list or if you have personal stories or photos you'd like to share, please e-mail us at w-lmk.webmaster@noaa.gov.  Please let us know if we may include your comments or experiences here on this page.


1.  The Summer of '36
July - August 1936
High Temperature Graph
The summer of 1936 is legendary for intense heat coupled with an extreme lack of rainfall.  While the entire first half of the year was unusually dry, true drought conditions developed with a vengeance in June.  Bowling Green suffered through the month with only twelve hundredths of an inch of precipitation, which still stands today as the third driest month on record, and the driest June ever.  Similarly, Louisville received only 0.35" of rain (driest June on record) and Lexington got 1.18" of rain (2nd driest June on record).

Then came the searing heat.  The last few days of June saw afternoon temperatures reach around 100 degrees, followed by a brief break in the heat for the first three days of July.  However, the hot weather had only just begun.  Every day from July 8 through 15 all major reporting stations in Kentucky reported 100 degree temperatures.  Louisville peaked at 107 on the 14th (their all-time high), Lexington hit 108 on the 10th and 15th (their all-time high), and Bowling Green struck 106 on the 10th and 11th.  At night temperatures dropped only into the upper 70s and lower 80s.

Hot summer weather continued for the rest of July, though not at record levels.  Then in August another heat wave swept the region from the 16th to the 28th.  Bowling Green recorded another ten 100 degree days during that stretch, peaking at 106 on the 28th.  Louisville topped out at 101 on the 19th and 22nd, and Lexington made it to 105 on the 19th (their all-time high for August).

The summer of '36 turned out to be the hottest summer ever recorded at Louisville, Lexington, and Bowling Green.  It was also the 2nd driest at Lexington, third driest at Louisville, and eighth driest at Bowling Green. 

Modern air conditioning had been invented in 1902, but didn't become commonplace in residential homes until the 1950s.

2.  Kentucky's Hottest Day
July 28, 1930
  Hot hot hot
While the summer of 1936 was known for its prolonged heat and drought, arguably the hottest single day in Kentucky history occurred several years earlier.  The map above (click on the image for a larger version) shows high temperatures from July 28, 1930.  Nearly everyone saw readings above 100 degrees.  The red values indicate all-time high temperature records set that day.

July and August of 1930 were extremely hot and dry.  Louisville recorded it's all-time driest July with only a quarter inch of rainfall.  July 28 was one of a lengthy string of extremely hot days, with many weather stations reporting temperatures well over 100 degrees for several days before the 28th and a couple of weeks after.  As a matter of fact, some of the stations that did not set all-time record highs on July 28 did set them in early August!

3.  1901 Heat Wave
July
At Bowling Green 30 of the month's 31 days had temperatures of at least 90 degrees, and 16 days saw at least 100 degrees.  Every day from the 20th to the 29th had a high of at least 102!  To add insult to injury, Bowling Green received a paltry 0.17" of rain, all of which fell within 48 hours!

Louisville experienced twenty-seven 90 degree days and eight 100 degree days (7 of them consecutive) including 107 degrees on the 24th, which is the all-time record high for the city.  Five of the record warm temperatures set during the month still stand today, over a century later, including the warm low temperature of 83 degrees on the 25th.  Fortunately, Louisville benefited from heavy thunderstorms on the 3rd that brought 2.19" of rain, though the rest of the month was quite dry.

Conditions weren't quite as bad at Lexington, which recorded only two 100 degree days and over three and a half inches of rain.

The July 1901 heat wave was widespread and deadly across much of the eastern United States, with over 9500 heat-related casualties nationwide -- 724 of them in New York City alone.

4.  Kentucky's Warmest Year
2007
 
Drought graphic
 

Kentucky drought

Harrodsburg, KY on 6/14/07

The Louisville office set 12 record warm temperatures in August 2007. The average for August is 77 degrees but this year the average was 85 degrees. Over the whole 2007 year, there were 67 days of 90 degrees or warmer and 5 of over 100 degrees.

At Louisville International Airport, there were 26 days of 90 degree or more temperatures in August. In Bowling Green there were 32 days. The eastern part of Kentucky was a bit cooler. In Lexington there were only 9 days that were 90 degrees or higher.

These high temperatures and lack of rain lead to a deficit in the early fall. Rain deficits around 15-20 inches were found over parts of the Commonwealth. The United States Drought Monitor rated most of Kentucky in extreme conditions. A federal disaster declaration was granted for the state of Kentucky where farmers were hit hard by the drought. All types of crops were affected from hay to corn to soybeans.

Photo by: Jordan Wirth

5.  1954 Extreme Drought
1954
rainfall deficit graph
The drought in 1954 is by far one of the worst droughts for Kentucky. The Central Region, Bluegrass, and Western Region of Kentucky were in the extreme drought category throughout the whole year while the Eastern Region reached severe category.

The graph above shows the PDSI (Palmer Drought Severity Index) for the Central Region of Kentucky. If the index is at 0 then the precipitation is normal for that month. At -2 that is a moderate drought, -3 is severe drought, and -4 is extreme drought.

In 1954 most of the Central Region was in extreme drought starting in January and continuing through October. In July, the Central Region only received 23.03 inches of rain where the average is 30.82, this producing a 7.79 deficit. By the end of 1954, the total rainfall was 40.97, a 7.72 deficit.


6. The 57 Day Drought
1921
 high temperature graph

71.9 degrees was the average daily high during the heat wave, and the warmest March on record was recorded in Bowling Green.

The warm trend continued into May with temperatures above normal and several days were above 90 degrees. In June the average daily temperature was 94 degrees with several days 5 to 10 degrees above normal.

July had the worst of the weather with the average daily high up to 97 degrees and the temperature rising to 90 or above every day within the month. Ten of the days had temperatures of 100 degrees or above. After 57 days of consecutive drought like weather, the streak stopped when temperatures reached 88 degrees on August 7th.

In Bowling Green, heat indices were well into the 100s almost every day, from the 30th of June to the 2nd of August, with daily high temperatures above 90 degrees for nearly one-third of the year.


7.  1991 Drought
1991
 '91 drought graph
  The 1991 Heat Wave was just as impressive as the 1990 but the only difference and the reason why 1991 made our top ten list is the fact that a drought was associated with it. The spring rainfall produced 11.42 inches which was only a deficit of 1.34 inches. But as summer approached, very little rain fell, with June through August only producing 7.57 inches of rain where the average should be 11.06 inches. This produced a deficit of 3.49 inches. When autumn approached the rain deficit  continued with only 6.92 inches falling, increasing the deficit to 7.01 inches overall.

The temperatures with the 1991 heat wave made the record books with 1991 both the 3rd warmest year (59.7 degrees Fahrenheit) and the 3rd warmest summer (Jun-Aug) with an average of 79.6 degrees. It is also the 2nd warmest spring (Mar-May) on record with an average of 60.9 degrees.


8.  Water Shortage and Drought
1983

Low Lake Cumberland

Lake Cumberland at low water level

1983 was known as the second worst drought to hit during the 20th Century. It was so dry that many trees and shrubs were forced into dormancy as well as many towns having water shortages. In Louisville alone, the July precipitation was only 0.99 inches which is well under the average of 4.30 inches. In August they received 2.39 inches of rain but that was still 1.02 under the average. Even in September there was a shortage of rainfall with Louisville only receiving 1.13 inches where the average is 3.05 inches. It wasn’t until October when the rain came. 6.47 inches of rain fell which is well above the average of 2.79 inches.

Besides having a lack of precipitation the temperatures where extremely warm. The average temperature for the summer (June-August) was 78.7 degrees Fahrenheit. August of 1983 ranked as the 6th warmest August with an average of 81.7 degrees. Most of July and most of August were over 90 degrees with July having 23 days and August having 27 days.

Photo by: John Beagle


9.  A Peak Heat in August
August 1900
 August calendar
1900 was a very warm year; in fact it is the 15th warmest year on record for Kentucky, as well as the 4th warmest fall. In July, the normal average monthly temperature is 78 degrees Fahrenheit, but in 1900 the average was 88.5 degrees. In August, the normal average is 77 degrees yet in 1900 the average was 82.5. Lastly, in September, the normal average is 70 degrees but the average that year was 75.4 in 1900.

At Louisville August 1900 has the most number of 90 degree days or higher than any other August on record. It has 29 days resulting in a max average of 93.6 degrees. As you can see with the calendar above, most days surpassed the normal average temperature per day which ranges 87-84 degrees. These 29 days and high average places August 1900 has the 3rd warmest August on record with only 2007 and 1936 ahead of it.


10.  A Warm Streak in June
1952

June temperatures

The 1952 heat wave lacked the intensity of other heat waves but it did have duration. According to the Kentucky Division of Forestry, numerous acres burned in 1952 due to the lack of precipitation. In Louisville alone, there was not a single day below the average temperature. According to the graph above June reached over 100 degrees two times and over 90 degrees twenty-one times. June of 1952 is the warmest June on record for Louisville.

In July 1952, the PDSI (Palmer Drought Severity Index) reached moderate levels. The drought was the beginning of the 1952-1955 extreme drought.

Created by: Stephanie Dunten & Tom Reaugh


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