A Record Breaking August for Indianapolis!

Central Indiana
August 2010 Climate Summary
5th Warmest on record at Indianapolis
Driest on record at Indianapolis
The month was dominated by a persistent high pressure ridge both at the surface and aloft. This resulted in many days with abundant sunshine and hot temperatures. High temperatures at Indianapolis exceeded 90 degrees on 16 days and exceeded 95 degrees on 7 days during August. For August, the number of days above 95 degrees was the second only to 1936 when 11 occurred. July 1988 was the last time Indianapolis experienced more days above 95 degrees when 10 occurred. Highs were at or above 80 degrees at Indianapolis every day of the month, the first time that has happened since August 2002.
Highs across central Indiana warmed into the mid and upper 90s on the 4th before a cold front brought temperatures back into the 80s through the 8th. The return of the upper ridge of high pressure then signaled the hottest stretch of the entire month, as many locations across central Indiana saw temperatures rise to 95 degrees or warmer for five consecutive days from the 9th through the 13th.  For the Indianapolis area, this was only the 17th such occurrence since weather records began in 1871. Such warm temperatures combined with high humidity levels produced heat indices of 100-110 degrees. The passage of another cold front early on the 15th provided a brief respite from the hot temperatures. However, slightly hotter weather returned once again on the 19th and 20th. A more significant cold front moved across central Indiana on the 21st, ushering in cooler and less humid conditions through the 27th.  Temperatures in rural areas of Indiana dropped into the middle to upper 40s and in urban areas into the 50s. For the urban areas, this was the coolest air in 8 weeks and since May some rural areas. The upper ridge returned for the last four days of the month and with much of central Indiana dry from very little rain since late July, high temperatures warmed quickly back into the lower and mid 90s. Lafayette recorded its warmest temperature of the summer at 95 degrees on the 29th.
The presence of higher humidity values helped keep overnight lows well above average for much of the month, especially at Indianapolis and at Eagle Creek Airpark. Low temperatures remained above 70 degrees at Indianapolis seventeen days out of the month.
August 2010 Avg Temp
August 2010 Difference from normal
Lowest Temperature
98 on 11
58 on 27
95 on 29
53 on 27
92 on 29
49 on 27
Terre Haute
98 on 4
48 on 27
97 on 4 and 12
46 on 27
94 on 4
47 on 27
Indy – Eagle Crk.
96 on 4 and 13
53 on 27
At Indianapolis, there were 4 days with below normal average temperatures, 25 days with above normal average temperatures and 2 days with normal average temperatures.
August 2010 was for the 5th warmest in the Indianapolis area since 1871.

August 2010 was reminiscent of the Great Indiana Drought of 1988 for central and southern Indiana. August 2010 was one of the driest months on record for portions of central Indiana. Monthly totals ranged from 0.25 inches to nearly 6 inches. This was less than 10% to nearly 200% of normal. Most areas received 0.50 to 3.50 inches for the month. As is typical of convective rainfall, amounts varied greatly over short distances.
Near record dry conditions occurred in an area of central and western Indiana south of I-74, west of I-65 and north of US highway 50. This dry area extended westward into Illinois. Most of this area received less than an inch of rain during August. The Indianapolis airport measured 0.37 inches of precipitation for the month, making it the driest August on record.
Most of the rainfall during August occurred from the 3rd through the 15th. The most significant rain of the month occurred during the evening of the 13th. In a 2 hour period, 3 inches of rain fell in the Lawrence area of northeast Marion County. Unusual local flooding was noted.
During the second half of August, rainfall of 0.25 to 1.50 inches occurred from late on the 20th through the 21st. Southwest and south central Indiana received the most rain during this period. After the 21st, nearly the entire state remained dry for the rest of the month.
The tropical conditions of July were replaced with desert-like conditions in August for many areas of central and southern Indiana. The afternoon heat caused crop stress and the lack of rain caused early maturity of many crop fields. Those areas north of Interstate 74 which received significant rain during August prospered.
The US Drought monitor of August 24 indicated abnormally dry conditions along and south of Interstate 74 in nearly all of Indiana. The Indiana Weekly Crop Progress and Condition Report released on August 30 indicated that nearly three-fourths of the state’s top soil and nearly two-thirds of the state’s subsoil was rated dry to abnormally dry.
August 2010 Precipitation
August 2010 Difference from Normal
Wettest Day
Longest Dry Stretch
0.18” on 21
7 days 22-28
0.98” on 4
4 days 5-8, 28-31
1.87” on 4
7 days 22-28
Terre Haute
0.50” on 21
8 days 22-29
0.45” on 21
10 days 22-31
0.90” on 11
10 days 22-31
Indy – Eagle Crk.
0.10” on 3
15 days 6-20
(*) – Precipitation data for Eagle Creek Airpark (KEYE) is missing for August 21.
August 2010 was the driest in the Indianapolis area since 1871.
Severe Weather
Scattered severe thunderstorms producing damaging winds affected mainly areas along and north of Interstate 70 during the afternoon and evening of August 4 in the vicinity of a cold front. A stalled out frontal boundary was responsible for scattered strong to severe thunderstorms on August 11. An isolated slow-moving thunderstorm on the evening of the 13th over the northeast Indianapolis metro area produced localized flooding in Lawrence.
For information on severe weather in other areas during August, visit the Storm Prediction Center “Severe Weather Event Summaries” website at http://www.spc.noaa.gov/climo/online/
At the Indianapolis International Airport, the peak wind gust this month was 36 mph from the northwest on August 4 as a line of thunderstorms passed through the Indianapolis metro area. Fog or haze was observed on 15 days. Thunderstorms were observed on 3 days during the month.
September 2010 Outlook
The official outlook for September 2010 from the Climate Prediction Center indicates a greater chance of above normal temperatures for central Indiana. At Indianapolis, the average temperature for the month is 66.3 degrees. The outlook calls for an equal chance of near, above or below normal precipitation. The average precipitation for September at Indianapolis is 2.88”.
Data prepared by the Indianapolis Forecast Office.

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