One Hot Summer - The Summer 2010 Climate Summary

Central Indiana
Summer 2010 Summary
As we begin the month of September, we mark the conclusion of meteorological summer and welcome meteorological autumn as nights become longer and the temperatures begin to cool. The summer of 2010 will go down as one of the warmest in recent memory across central Indiana. After a very wet and stormy June, increasingly drier conditions were experienced through July and August. The following is a summary of weather conditions experienced in Central Indiana during the months of June, July, and August 2010.
At Indianapolis, high minimum temperature records of 78 degrees were tied on July 23 and August 10. The high of 96 degrees on August 15 tied the record for that day. 1.95 inches of rain fell on June 21, setting a new record rainfall for the day. 
The summer of 2010 was the 4th warmest summer ever at Indianapolis and the warmest since the summer of 1934, with an average temperature of 78.1 degrees. The normal summer average temperature is 73.5 degrees, making this summer above normal by 5.5 degrees. This summer was noted for its warm nighttime lows, and the average minimum temperature of 68.6 degrees ended up being the 5th warmest for a summer season.
High temperatures started in the mid and upper 80s right away to begin the month with lows only falling into the mid 60s for most locations. In the wake of a cold frontal passage early on the 6th, highs fell back into the 70s through the 8th as a cooler and less humid airmass arrived in central Indiana. As southerly flow reestablished by the 9th, high temperatures recovered back into the 80s. In fact, high temperatures would not fall back below 80 degrees for most of the region again until the 29th as a very warm and humid airmass would remain not only across central Indiana, but much of the Midwest for the bulk of the month. The first 90 degree day of the year came for much of the region on the 11th, with several to follow as the month progressed. Indianapolis made it to 90 degrees officially five times during the month. The high exceeded 80 degrees on 25 of the 30 days at Indianapolis, and was at or above 85 degrees on 15 of the 30 days during June.
After the 10th, low temperatures largely remained at or above 65 degrees for most of the rest of the month as the humid airmass and plenty of moisture from rainfall through the month kept temperatures higher at night. The low remained at or above 70 degrees at Indianapolis eight times during the month, and at or above 65 degrees 25 of the 30 mornings.
This was the seventh warmest June on record in terms of average temperatures at Indianapolis, and the warmest on record since June 1952 when the average temperature topped out at 76.5 degrees.


The month started off on a cooler note, with below average temperatures experienced at most locations on the first few days of the month. Those dates saw low temperatures in the 50s, something that would not be seen again at most areas for the remainder of the month. Just a few days later, hot and humid conditions moved into Central Indiana and these conditions would prevail for most of the rest of the month. Even on days with scattered showers and thunderstorms, temperatures had time to reach above average.

Most areas saw temperatures at or above 90 degrees on about a third of the days during the month. At Indianapolis, 11 days of 90 or above were recorded. A typical July in Indianapolis has 7 days of 90 degrees or higher. For June and July, Indianapolis has had 16 days of 90 or higher, compared to an average of 11 days in a typical year. The highest temperature recorded during the month at many locations was around 93 degrees. At Indianapolis, the high temperature for the month of 93 degrees was the warmest temperature seen in a July since 2006.

The hot and humid airmass kept temperatures well above average during the night. Across much of Central Indiana, over a third of the month had low temperatures at or above 70 degrees. At Indianapolis, the average low temperature during July 2010 ranked the 11th warmest. Indianapolis tied the record of 78 degrees for the warmest minimum temperature on July 23. The original record for the date was set in 1933.
This was the 15th warmest July on record in terms of average temperatures at Indianapolis, and the warmest July on record since July 1999 when the average temperature topped out at 79.2 degrees.
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.  This was the 5th warmest August on record at Indianapolis, with an average temperature of 79.5 degrees.
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.
Temperature Data for Other Sites in Central Indiana
Summer 2010 Temperature
Normal  Temperature
Diff. From Normal
Indianapolis Int’l Arpt
Terre Haute
Indianapolis – Eagle Creek
Summer Extremes Across Central Indiana
Warmest Temperature
Coldest Temperature
Indianapolis Int’l Airport
98 on 8/11
56 on 6/30
95 on 8/29
53 on 6/30, 7/1 and 8/27
93 on 7/7
49 on 8/27
Terre Haute
98 on 8/4
48 on 8/27
97 on 8/4 and 8/12
46 on 8/27
94 on 8/4
47 on 8/27
Indianapolis-Eagle Creek
96 on 8/4 and 8/13
53 on 8/27
Overall this was the 45th wettest summer on record. The total rainfall for Indianapolis this summer was 12.97 inches. The normal rainfall total for summer is 12.37 inches, which made this fall above normal by 0.60 inches.  Much of the rainfall received during the summer season fell during the month of June, when many locations were three to six inches above normal. Indianapolis experienced the third wettest June in recorded history, as 9.73 inches of precipitation fell. July and August were progressively drier, with many locations in central Indiana receiving less than three inches of rainfall during the month of August. Indianapolis experienced the driest August on record with just 0.37 inches of rainfall. Due to the excessive rainfall during June across much of central Indiana, many locations still finished the summer three to five inches above normal.
Monthly rainfall during June in central and southern Indiana varied from 4 inches to over 15 inches. Nearly 90% of the area received 6 to more than 15 inches...with one-third of the area receiving more than 10 inches. This was 150% to more than 600% of normal.   Typically central Indiana receives around 11 inches of rain during the summer. This June one-third of central Indiana received a summer’s worth of rain in less than four weeks. At Indianapolis, 9.73 inches fell making it the third wettest June on record.
A seemingly endless parade of storms continually dumped rain, sometimes heavy, on central Indiana. The longest “dry spell” between storms was less than 3 days. Because May was on the wet side, the widespread nature of this rainfall had almost an immediate impact on area rivers. Most rivers reached bankfull levels early in June and continually rose higher after each rain. Because the rainfall was distributed over a four week period, historic river flooding as experienced in June 2008 did not occur. Flooding occurred along almost every river in central Indiana.   River flood levels were the highest since late May 2009.   Flooding along the White and Wabash Rivers in southwest Indiana and southeast Illinois continued into July.
The worst flooding during the month occurred on the 22nd. Portions of central Indiana received up to 4 inches of rain during the night of the 21st. Because this area had already received nearly 2 inches of rain in the previous 72 hours, serious flash flooding occurred in portions of Clinton and Hendricks Counties. Nearly the entire town of Edna Mills in northeast Clinton County was flooded including State Road 26. In Hendricks County, two small dams located in the White Lick Creek drainage area were compromised. This caused the evacuation of a nearby mobile home park located along White Lick Creek just downstream of the dams. County and state roads near the creek were flooded in the Avon, Plainfield and Mooresville areas. High water affected the Crystal Bay area near Hummel Park in Plainfield.
The abundant and prolonged rainfall impacted the agricultural community.   Fields that did not drain properly had uneven growth patterns. The nearly constant high humidity levels delayed wheat harvest and hay cutting. Some agricultural lands will remain fallow this season because they will not dry out in time to plant a crop.
Monthly rainfall during July in central and southern Indiana varied from slightly over 1 inch to more than 10 inches.   This was 25% to more than 200% of normal.   The wet pattern of June continued in July for much of the western portion of Indiana.  This was not true for portions of eastern Indiana.   After receiving nearly 14 inches of rain during June, one location in Rush County measured only 1.50 inches during July.

The dry period at the end of June continued through the morning of the 8th.   Once again, a prolonged unsettled weather pattern returned to central Indiana and continued through the end of July.  The longest dry spell across the entire central and southern Indiana area was less than 3 days.  Nearly daily afternoon and evening thunderstorms occurred.  As is typical of convective rainfall, amounts varied greatly over short distances and coverage was not often widespread.  Rainfall from these storms was quite intense at times.  Several locations received 2 to more than 4 inches in a 3 to 6 hour period. 

Localized flooding did occur during July in several areas of Indiana.  The coverage and duration of the heavy rain was much less than in June.  As a result, localized flooding lasted less than 12 to 24 hours.  The heaviest rain in central and southern Indiana occurred during the evening of 17th when 3 to nearly 6 inches fell in portions of Owen and Greene Counties.  The White River in Greene, Knox and Daviess Counties reached bankfull levels as a result.

The tropical conditions of July provided Indiana field crops excellent growing conditions.  The frequent and at times abundant rainfall aided crop growth especially in much of western Indiana.  Crops in dry areas like portions of Rush County suffered during the afternoon sun.  The dry spell in early July allowed farmers to replant many areas flooded during June.
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 70 in nearly all of Indiana. The Indiana Weekly Crop Progress and Condition Report released on August 30, 2010 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.
Rainfall Data for Other Sites in Central Indiana
Summer 2010 Rainfall
Normal Rainfall
Diff. From Normal
Indianapolis Int’l Arpt.
Terre Haute
Indianapolis – Eagle Creek
(*) – Precipitation data for Shelbyville (KGEZ) is missing for June 22.
(**) – Precipitation data for Eagle Creek Airpark (KEYE) is missing for August 21.
Major Weather Events
The first significant bout of severe weather during the summer season occurred during the early morning of June 6 as an unusually strong low pressure system moved across the lower Great Lakes. Numerous supercell thunderstorms producing damaging winds and tornadoes developed over northern Illinois during the evening of June 5 before migrating into north central Indiana after midnight. One of the supercells produced two EF0 tornadoes over Carroll County, causing some structural damage in Yeoman.
The majority of the severe weather during June across central Indiana took place between June 12 and 22 as a frontal boundary remained in the vicinity of the region. This included severe storms producing an EF0 tornado in Paragon in Morgan County on the evening of the 12th, two intense bow echo lines of thunderstorms moving across the region and producing widespread wind damage on the 14th and again on the 15th, and additional severe thunderstorms producing flooding during the evening of the 18th and the early morning of the 19th. The culmination of this very busy stretch with waves of thunderstorms producing severe weather and flooding came on the evening of the 21st and early morning of the 22nd as central Indiana was affected by three significant thunderstorm clusters over about a 12 hour period. Initially, these storms produced damaging winds and constant cloud-to-ground lightning but as heavy rain continued to fall, the focus during the early morning of the 22nd shifted to flash flooding across much of the region. Much of central Indiana received 3 to 4 inches of rain from sunset on the 21st through daybreak on the 22nd, and this led to several instances of flash flooding across the region.
Thunderstorms produced scattered wind damage on July 16, with trees knocked down the most common report. On July 17, severe storms produced 70 mph winds in the Lafayette area, downing numerous trees and causing damage to some homes. Heavy rain also fell that day, with over 6 inches of rain reported at Shakamak State Park.
A tornado touched down near Trafalgar in Johnson County on July 20. The tornado was rated EF0, and it produced damage including several trees snapped in half or uprooted, damage to a shed where the tin roof was littered into an open field, and tin siding embedded into the ground. Just a couple of days later, on July 22nd, another EF0 tornado touched down in Johnson County, this time near Greenwood. This tornado downed tree limbs, damaged roofing of some sheds, and flattened small areas of crops. 
Autumn 2010 Outlook for Central Indiana
The official outlook for the 2010 autumn season (September-November) from the Climate Prediction Center, indicates a greater chance of above normal temperatures across central Indiana. At Indianapolis, the average temperature for the autumn season is 54.6 degrees. An equal chance of above, below or near normal precipitation exists across central Indiana through the fall. At Indianapolis, the average precipitation for the autumn season is 9.25” and the average snowfall is 1.7”.
Data prepared by the NWS Indianapolis Climate Team
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