August 2013 Climate Summary

Central Indiana
August 2013
Climate Summary
Tied for 43rd Warmest on record at Indianapolis
12th Driest on record at Indianapolis
The summer season wrapped up with temperatures generally near to slightly below normal for most of central Indiana in August. Temperatures were seasonable for the first part of the month with highs mainly in the lower and middle 80s and lows in the 60s. The passage of a cold front on the 12th ushered in a fall-like preview with a much cooler airmass as a broad upper trough established over the Great Lakes. High temperatures from the 13th through the 16th fell back into the 70s across central Indiana, with some locations even struggling to make it to 70 degrees on the 14th. Lows fell into the 40s in rural locations with clear skies and light northerly flow.
Temperatures began to modify on the 17th, with highs returning into the middle and upper 80s through the 25th as the upper trough moved away to the east, allowing warmer and more progressively humid conditions to expand into the Ohio Valley. Highs exceeding the 90-degree mark returned for the first time in nearly five weeks beginning on the 26th as the upper ridge across the central U.S. expanded east into the region. Despite a weak boundary dropping through central Indiana on the 28th, the ridge would remain the dominant feature to end the month with many locations experiencing highs in the lower to middle 90s every day from the 26th through the 31st. Many locations along and south of Interstate 70 experienced their hottest temperatures of the year on the 31st. This included Indianapolis, which recorded a high of 96 degrees on the last day of August, 1 degree shy of the daily record. The six days of 90+ degree temperatures to end the month enabled Indianapolis to finish slightly above normal for August.
August 2013     Avg Temp
August 2013 Difference from Normal
Lowest Temperature
96 on 31
52 on 14 and 15
93 on 30
47 on 15
92 on 27
45 on 14 and 15
Terre Haute
96 on 31
47 on 15
95 on 31
45 on 15
73.2 (*)
97 on 31
48 on 15
Indy – Eagle Crk.
93 on 31
50 on 14
 (*) Temperature data was not available on August 11 at Shelbyville                       
At Indianapolis, there were 18 days with above normal average temperatures,10 days with below normal average temperatures and 3 days with a normal average temperature.
August 2013 was tied for the 43rd warmest in the Indianapolis area since 1871.

August was a dry month for much of Indiana. Monthly rainfall totals ranged from around a tenth of an inch in south central Indiana to over 6 inches in northwest Indiana. Much of the state received one-half to 3 inches during August.  Rainfall during August was sporadic in central and southern Indiana. Only two relatively heavy rainfall events occurred. On the 8th, southeast Marion and northwest Shelby counties received 1.5 to nearly 3 inches of rainfall that caused localized flooding. On the 20th, a small portion of southwest Jackson County received 1 to 2 inches of rain.
The only elevated river levels during August occurred along the Wabash River from the 4th to the 9th in the Lafayette and Covington areas as a result of significant upstream rains. Much of northern Indiana received one-half to more than 4 inches of rain on the 2nd. The heaviest rainfall was concentrated in the Columbia City and Huntington areas located in the upper northeast portion of the Wabash watershed.
A prolonged dry spell began in much of central Indiana around the 10th and continued for much of the remainder of the month.  Little or no rain fell in all Indiana for the 7 day period ending 8 am EDT on the 20th. The Indianapolis airport received no measurable rainfall from the 10th through the 30th. Trace amounts did fall on the 10th, 16th and 28th. This was the first extended dry period of the summer and the longest since June–July 2012. More widespread thunderstorms impacted northern portions of central Indiana on the evening of the 30th as a weak upper level disturbance passed through the region. Many locations, especially along and south of Interstate 70, received generous rainfall on the afternoon and evening of the 31st as strong to severe thunderstorms impacted the region. One to two inches fell in several locations over southern portions of central Indiana.
The U.S. Drought Monitor indicated that abnormally dry conditions existed in much of central Indiana as of August 27th.   The U.S. Geological Survey Water Watch indicated below normal stream flow for the 7 day period ending August 28 in much of central and southern Indiana. This included the entire Wildcat Creek watershed, all of the White River downstream of Indianapolis and the entire East Fork White River. Local reservoirs were approaching a foot below normal levels.
August 2013 Precipitation
August 2013 Difference from Normal
Wettest Day
Longest Dry Stretch
0.71 on 3
 11 days 17-27
0.52 on 8
 7 days 23-29
0.93 on 3
 11 days 11-21
Terre Haute
1.01 on 8
 9 days 13-21
1.22 on 31
 8 days 23-30
1.71 on 8
 11 days 11-21
Indy – Eagle Crk.
0.70 on 31
 17 days 11-27
August 2013 was the 12th driest in the Indianapolis area since weather records began in 1871.
Severe Weather
Little severe weather occurred across central Indiana in August, primarily being confined to the last day of the month. Thunderstorms impacted much of the northern half of central Indiana during the evening of the 2nd and early morning of the 3rd ahead of a cold front and again on the 8th across mainly areas along and south of Interstate 70 in advance of a wave of low pressure. Scattered thunderstorms impacted much of the northern portions of central Indiana on the evening of the 30th, producing locally heavy rainfall, gusty winds, small hail and dangerous lightning which impacted outdoor events.
Thunderstorms once again erupted during the afternoon of the 31st as an upper level wave moved through the region, producing severe weather for the first time in five weeks across the region. The storms gradually shifted south across central Indiana through the evening, impacting much of the region along and south of the Interstate 70 corridor. Outdoor events on the holiday weekend were once again affected by the weather, as storms exhibited plenty of cloud to ground lightning strikes and locally torrential rainfall. Several thunderstorms also produced large hail and damaging winds, particularly across Putnam and Vermillion Counties, and also across the western Indianapolis metro area during the late afternoon. Thunderstorms continued to produce gusty winds which knocked trees and limbs down through the evening, particularly across Knox County and near Vincennes.
For information on severe weather in other areas during August, visit the Storm Prediction Center “Severe Weather Event Summaries” website at
The maximum wind gust at Indianapolis International Airport was 44 mph out of the northeast on the 31st associated with strong to severe thunderstorms in the Indianapolis metro area. Fog or haze was reported at Indianapolis on 18 days during the month, with dense fog occurring on the 7th. Thunder was reported on 4 days in August.
September 2013 Outlook
The official outlook for September 2013 from the Climate Prediction Center indicates an equal chance of near, above or below normal temperatures for central Indiana.  At Indianapolis, the average temperature for the month is 66.9 degrees. The outlook also calls for a greater chance of above normal precipitation. The average precipitation for September at Indianapolis is 3.12”.
Data prepared by the Indianapolis Forecast Office.

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