Central Indiana Summer 2012 Climate Summary

Central Indiana
Summer 2012 Summary
The summer of 2012 will go down as one of the hotter summers in recent memory across central Indiana, with numerous temperature records broken. Indianapolis International Airport exceeded the century mark nine times during the course of the summer, the most 100 degree days on record since the summer of 1936 when the century mark was topped 12 times. Additionally, the temperature reached or exceeded 90 degrees on 48 days during the summer months in Indianapolis, more than three times the normal.
The 2012 summer was also noted for the exceptionally dry weather experienced for much of central Indiana during June and July exacerbating significant drought conditions. Indianapolis received only 0.92 inches of precipitation total during June and July, easily setting a new mark for the driest June and July period on record. Many locations across central Indiana however experienced above normal rainfall in August, easing drought conditions somewhat. The following is a summary of weather conditions experienced in Central Indiana during the months of June, July, and August 2012.
The summer of 2012 was tied for the 5th warmest summer ever at Indianapolis, with an average temperature of 77.8 degrees. The normal summer average temperature is 73.9 degrees, making this summer above normal by 3.9 degrees.  The average temperature of 77.8 degrees was also just 0.3 degrees cooler than the average temperature experienced during the summer of 2010, and 0.2 degrees warmer than the average temperature from the summer of 2011.
While the month started out exceptionally cool as an upper level low meandered across the Ohio Valley, June 2012 will be remembered most for the historic heat that arrived at the end of the month, culminating with highs in the lower to middle 100s on the 28th and 29th. 
As mentioned above, cool, cloudy conditions with scattered rain showers accompanied an upper level low as it moved across the region on the 1st and 2nd. Low temperatures in the middle and upper 40s were common the first few mornings of the month as well. Temperatures recovered slowly over the next few days as much of the lower Great Lakes and Ohio Valley remained in northerly flow on the back side of the upper disturbance. High temperatures returned into the upper 80s and lower 90s from the 8th-10th as an upper ridge expanded into the Ohio Valley.
A consistent pattern began to develop by the middle of the month as upper level ridging would expand into the region for a few days producing above normal temperatures, before a weak frontal passage would bring the temperatures back down to near or slightly below normal with the upper ridge shifting back to the south and west. The presence of predominant surface high pressure and steadily worsening drought conditions across the Ohio Valley enabled increasingly hotter temperatures each time the upper ridging returned. After the 14th, high temperatures were rarely cooler than the upper 80s and lower 90s for much of central Indiana. 
The expansion of a strong upper ridge brought historic heat to central Indiana beginning on the 28th and continuing through the end of the month. The record high monthly temperature for June at Indianapolis was broken on the 28th when the temperature at Indianapolis reached 104 degrees, making it the warmest day in Indianapolis in nearly 58 years. The last time the Indianapolis area reached 104 degrees was on July 14, 1954. Temperatures were sweltering aranged from 102 to 107 degrees across all of central Indiana on the 28th, followed by highs in the upper 90s to middle 100s on the 29th and in the 90s to around 100 on the 30th. Indianapolis set a new record high on the 29th as well when temperatures made it to 103 degrees. This also marked only the second time in recorded history that Indianapolis had experienced consecutive days at or above 100 degrees in the month of June. The only other occurrence took place from June 28-30, 1934. Indianapolis finished the month by tying the record high for the 30th of 97 degrees from 1911. 
There were fifteen days at or above 90 degrees at Indianapolis through May and June, marking the most 90 degree days prior to July 1 since 1988 when the mercury hit 90 degrees 17 times in May and June. June also wrapped up the warmest first six months of the year on record for Indianapolis with an average temperature of 54.4 degrees, a full degree warmer than the previous record holder from January-June 1880. 
The hot, record breaking summer continued into July across central Indiana as an upper level ridge dominated much of the central US and the Ohio Valley for large stretches of the month. The worsening drought conditions across Indiana further contributed to warmer temperatures that exceeded 90 degrees on 28 days during the month at Indianapolis, and 95 degrees a whopping 18 times. Even more impressive was that the mercury reached 100 degrees on seven days at Indianapolis. This led to not only the warmest July on record, but the hottest month in recorded history at Indianapolis with an average temperature of a whopping 84.0 degrees. At other locations across central Indiana, Terre Haute led the way with an amazing 12 days at or above 100 degrees, with both Bloomington and Lafayette matching Indianapolis with 7 days at or above the century mark.
The hottest stretch of the month for central Indiana commenced on Indepedence Day as temperatures surged into the lower 100s, providing many locations with one of the warmest 4th of Julys on record. This began a string of four days with temperatures topping out above the century mark, highlighted on the 6th and 7th by highs that reached 105 and 106 degrees in many locations. In Indianapolis, the official high of 105 on both the 6th and 7th came within one degree of tying the all-time record high of 106 degrees, set on July 22, 1901, July 21, 1934, and July 14, 1936. Many locations across central Indiana experienced temperatures that topped out. Temperatures topped out above the century mark a few more times between the 17th and 25th.
Temperatures remained warm at night too, as overnight lows remained above 70 degrees for long stretches throughout the month. Indianapolis experienced a low temperature of 81 degrees on the 7th, marking the first time the low had stayed above 80 degrees at Indianapolis since August 22, 1936. Indianapolis never saw the temperature drop below 70 degrees at night until the morning of the 20th. With the exception of lows of 61 degrees on the 21st and 62 degrees on the 29th, temperatures did not drop any lower than 68 degrees throughout the month.
Below is a list of temperature records for Indianapolis reached during July, with old records following in parenthesis, during what will remembered as a historic month for heat not just in Indianapolis but throughout central Indiana.
•           Hottest Month on Record – 84.0 Degree Avg Temp (82.8 – July 1936)
•           Hottest Max Temp Avg on Record – 95.6 Degree Avg Temp (93.7 – July 1936)
•           Number of 90-Degree Days in a Month – 28 Days (25 Days – July 1901)
•           Number of 95-Degree Days in a Month – 19 Days (16 Days – July 1936)
•           Consecutive Days with Lows at or Above 70 Degrees – 22 Days: June 28-July 19 (20 Days: June 26-July 15, 1921)
The previous pattern of hot days continued for the first several days in August, with temperatures in the 90s. Some locations even reached 100 degrees. Terre Haute reached 100 on August 2 and August 8. At Indianapolis, the high temperature of 98 degrees on August 8th tied the record for the date.
However, a big change occurred by the 10th, as a potent cold front brought below average temperatures to the area. Temperatures averaged normal or below normal for much of the period from August 10 to August 22. That period at Indianapolis was the longest stretch of normal or below normal average temperatures since February 2010. During this period, some locations in central Indiana saw low temperatures in the 40s.
The string of consecutive 80 degree or higher maximum temperatures at Indianapolis was broken on August 10, when the high only reached 77 degrees. The string of 64 days that began on June 7 is the second longest stretch of consecutive 80 degree or higher maximum temperatures for Indianapolis, second only to the 86 day stretch in 2002.
Normal to above normal temperatures returned for the last third of the month, with highs in the 80s and 90s.
Temperature Data for Other Sites in Central Indiana
Summer 2012 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
105 on 7/6 and 7/7
48 on 6/2
103 on 7/7
45 on 6/2
106 on 6/28
46 on 6/6
Terre Haute
106 on 6/28, 6/29, 7/6 and 7/7
47 on 6/6
106 on 7/7
45 on 6/6
105 on 7/6 and 7/7
48 on 6/2
Indianapolis-Eagle Creek
103 on 6/28
48 on 6/2
Overall this was the 24th driest summer on record at Indianapolis. The total rainfall for Indianapolis this summer was 7.43 inches. The normal rainfall total for summer is 11.93 inches, which made this summer below normal by 4.50 inches.  
June was the driest month in over a hundred years in portions of central and southern Indiana. Monthly rainfall totaled from virtually nothing in portions of central Indiana to nearly 6 inches in northwest Indiana. Much of central and southern Indiana received less than an inch of rainfall for the entire month of June. Normal rainfall for June is 4 to 5 inches.
Rainfall at the Indianapolis airport totaled only 0.09 inches for the month of June.   This was the driest month for the Indianapolis area in over 100 years and the second driest of record. The driest month of record is March 1910 with only 0.07 inches. The previous driest June of record was 0.36 inches during the Great Drought of 1988.
Very little rainfall occurred in much of central and southern Indiana during the first 4 weeks of June. During this time only isolated areas received significant rainfall.   Portions of west central and northwest Indiana received as much as 3 to 5 inches of rainfall during the evening of the 16th.  After the 28th, storms brought much needed rainfall to areas of central Indiana located primarily north of I-74.
Drought conditions expanded during June. The U.S. Drought Monitor on June 26th indicated nearly 70% of the state in severe to extreme drought. Burning bans were noted for nearly all Indiana counties. At the very end of June, drought conditions were improving slowly in some of the driest areas of northeast Indiana as the result of recent rains. Conditions in southwest Indiana continued to worsen because of the historic heat wave at the end of June.
Stream levels in much of central and southern Indiana had fallen to record or near record low levels for late June. The Indiana Department of Natural Resources issued warnings to local boaters because local reservoirs were so low for the height of boating season. Crop yields in much of the state will be reduced because of the drought. Numerous wildfires broke out in the later portion of the month, very unusual for June in Indiana. Many communities requested voluntary water conservation. At least one local water company fined violators for ignoring its mandatory restriction on outdoor watering.
July was among the driest months of record portions of central and southwest Indiana to one of the wettest in isolated areas of south central Indiana. Monthly rainfall totaled from around one-quarter of an Indiana in portions of Boone, Putnam and Hendricks Counties in central Indiana to nearly 10 inches in portions of Crawford County in extreme south central Indiana.
The wetter areas of the state included northern and central Indiana north of a line from Chicago to Cincinnati and south central Indiana received mostly 2 to 5 inches of rainfall during July. The remainder of Indiana measured generally 1 to 2 inches. Normal rainfall for July is 3 to 5 inches. Rainfall during the first half of July was much more scattered that during the second half of July.
Measurable rainfall did not occur at the Indianapolis airport until the 18th.   This marked the driest start ever to the month of July for the Indianapolis area and driest 47-day period of record with only 0.09 inches of rainfall. The combined precipitation of 0.92 inches that fell at Indianapolis during the months of June and July, set a new record for the driest June and July, shattering the old mark of 2.45 inches that fell in June and July 1930.
Drought conditions expanded during July. The U.S. Drought Monitor on July 17th indicated nearly 90% of the state in severe to extreme drought. The following week the U.S. Drought Monitor indicated nearly 20% of the state was in the exceptional drought.   Burning bans were noted for nearly all Indiana counties. As July drew to a close, drought conditions improved in portions of extreme northern, south central and southeast Indiana with little change in the exceptional drought areas of central and southwest Indiana.
Streamflow in much of central and southern Indiana remained at seasonally record or to near record low levels for the entire month of July. Water sources were a concern for livestock operations as many creeks and ponds dried up during the month. Crop yields in much of the state will be reduced because of the drought. Numerous wildfires broke out during July, very unusual for July in Indiana. The state of Indiana requested voluntary water reductions in all areas. Mandatory water restrictions on outdoor watering remained in place in the City of Indianapolis and many nearby metropolitan areas.
There was dramatic change in the rainfall pattern from July to August. Some very dry areas of west central Indiana received over 10 inches of rainfall during August, while areas of south central Indiana that received over 8 inches in July turned much drier and received slightly over an inch of rainfall.   During August the big winners on the rainfall were many areas in the extreme to exceptional drought areas of west central and southwest Indiana.
The wet areas during August included much of central, northern and southwest Indiana. Many locations in these areas received 3 to more than 8 inches of rainfall. Extreme northern Indiana and most locations in south central and southeast Indiana missed out on most of this beneficial rainfall. These areas received only 1 to 3 inches of rain for the month. Normal rainfall for August is between 3 and 5 inches. 
Rain occurred numerous times during August, but areal coverage was never widespread. There were four significant rain events in central Indiana. Rain of 1 to 4 inches fell on the 4th-5th, 8th-9th, 16th-17th and the 27th.   The driest period during August was from 18th through 26th. Little or no rain occurred in much of the state except during the evening of the 20th. Isolated rains of up to an inch fell primarily north of I-70.
Drought conditions improved in most sections of central and northern Indiana and remained nearly the same or became worse in southern Indiana.   Although local area reservoirs remained below capacity, stream flow returned to normal in several areas of central Indiana, especially in the Indianapolis area. Near to record low levels continued in the East Fork White River Basin of east central and southern Indiana. 
Rainfall Data for Other Sites in Central Indiana
Summer 2012 Rainfall
Normal Rainfall
Diff. From Normal
Indianapolis Int’l Arpt.
Terre Haute
Indianapolis – Eagle Creek
Major Weather Events
With the ongoing dry conditions, severe weather events were extremely limited across central Indiana during the month of June. A complex of severe thunderstorms producing significant damaging winds otherwise known as a derecho, developed during the morning of the 29th over northern Illinois and then quickly intensified and sped southeast through the northern half of Indiana during the afternoon. These storms produced wind gusts of 60 to 70 mph across northern portions of central Indiana, along with blinding rainfall, large hail and an abundance of lightning. The storms dropped an outflow boundary with 55 to 60 mph wind gusts that quickly moved south across the Indianapolis metro area and many other parts of central Indiana and away from the storm complex. This derecho continued on to the southeast through the evening of the 29th, producing widespread wind damage over Ohio, West Virginia and portions of the Mid-Atlantic region. For a radar image composite of the June 29th Derecho, please go to:
Localized strong to severe thunderstorms occurred on several days throughout the month. The events that impacted the largest portions of central Indiana took place on the afternoon of the 8th, the afternoon and evening of the 19th, the morning of the 24th, and the afternoon and evening of the 27th. Damaging wind gusts were most common from these storms, with some reports of large hail as well. The thunderstorms often provided generous and much needed rainfall as well.
The cold front that brought the return to cooler air to central Indiana also brought severe weather in the form of damaging winds and large hail on August 9. Hail the diameter of billiard balls fell near Flora in Carroll County on August 9, and some buildings were damaged by winds in Carroll County as well. More information on this event can be found at:
Another cold front brought additional large hail, damaging winds, and heavy rain on August 16.
For information on severe weather in other areas throughout the summer, visit the Storm Prediction Center “Severe Weather Event Summaries” website at http://www.spc.noaa.gov/climo/online/.
Fall 2012 Outlook for Central Indiana
The official outlook for the 2012 fall 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 fall season is 55.2 degrees. An equal chance of above, below or near normal precipitation exists across central Indiana through the summer. At Indianapolis, the average precipitation for the fall season is 9.94” and 1.1” of snowfall.
Data prepared by the NWS Indianapolis Climate Team
Questions should be referred to w-ind.webmaster@noaa.gov

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