climate and environment

This map shows the risk level from air pollution in each neighborhood in comparison to the rest of Central Indiana. Risk is based on the toxicity and amount of emissions and the number of people nearby.

EXPLORE MAP

Temperature

Average temperature since 1948

The line chart shows the high, low, and average temperature of Indianapolis between the years of 1950 and 2020. The lows average between 40 and 45 degrees Fahrenheit. The highs average between 60 and 65 degrees Fahrenheit.
Source: NOAA National Centers for Environmental Information Get the data
Icon showing wavy heat lines.

63° 

Average high temperature

Icon showing snow flakes.

44° 

Average low temperature

  • April 17 Average last frost date
  • October 16 Average first frost date
  • 182 days Growing season

Temperature records

  • 106° Hottest day on record (Tuesday, July 14, 1936)
  • -27° Coldest day on record (Wednesday, January 19, 1994)
  • 55.4° average Hottest year on record (1921)
  • 48.3° average Coldest year on record (1917)
  • May 27, 1961 Latest freeze
  • September 30, 1899 Earliest freeze

Precipitation

Annual Precipitation

The line chart shows the annual precipitation in Indianapolis between the years of 1950 and 2020. The average is just above 40 inches per year.
Source: NOAA National Centers for Environmental Information Get the data

Annual Snowfall

The line chart shows the annual snowfall in Indianapolis between the years of 1950 and 2020. The average is between 20 and 25 inches per year.
Source: NOAA National Centers for Environmental Information Get the data

Annual Averages

Icon showing a rain cloud with a partial segment of sun peaking out behind it.

42.4 inches Average annual precipitation

Icon showing a large snow flake.

25.9 inches Average annual snowfall

  • 13 Extreme precipitation events per year (two inches or greater)
  • 6 Heavy snow events per year (two inches or greater)
  • 39 percent of precipitation is snow

Precipitation Records

  • 12.5 inches Maximum snowfall in 24 hours (Feb. 24-25, 1965)
  • 13 days Most consecutive rainy days (Apr. 9-21, 1893)
  • 39 days Most consecutive days without rain (Aug. 14-Sep. 22, 1908)
  • 7.2 inches Most precipitation in one day (Sep. 1, 2003)
  • July, 2015 Wettest month (13.1 inches of rain)
  • March, 1910 Driest month (0.07 inches of rain)
  • 1876 Wettest year (57.5 inches of rain)
  • 1934 Driest year (24.97 inches of rain)

Environment

Particle pollution can cause lung damage, asthma, and early death. These particles are created from point-source pollution, like power plants and factories, and from non-point-sources, such as agricultural dust and vehicle exhaust.

Indianapolis’ particle pollution has improved over the decades. Improved fuel efficiency and emissions for vehicles have helped, as well as conversion away from coal power plants. The recommended annual average for particle pollution is below 12 micrograms per cubic meter.

Particulate Matter in Midwestern Cities

The line graph shows the particulate matter levels in the air in Midwestern cities, including Indianapolis, Cincinnati, Cleveland, Columbus, and Chicago. Indianapolis has average more than the other cities.
Source: EPA Get the data

Micrograms per cubic meter of PM2.5 (particle 2.5 micrometers or smaller) in metro areas

Ozone is smog. It is created when pollution from vehicles, power plants, and industrial facilities react with heat and sunlight. Ozone is more common on hot summer days.

Ozone levels of 0.08 parts per million can cause a wide range of respiratory effects, and 0.072 parts per million can cause “decreased lung function and increased respiratory symptoms,” according to the Environmental Protection Agency.

Ozone levels have declined in the past decades but have been rising slowly since 2013. This is similar to other midwestern peers.

Ozone in Midwestern Cities

The line graph shows the ozone levels in the air in Midwestern cities, including Indianapolis, Cincinnati, Cleveland, Columbus, and Chicago. Indianapolis ranks on par with the other cities.
Source: EPA Get the data

Parts per million of ozone (O3) in metro areas

Water Quality in Streams, Lakes, and Aquifers

There are dozens of substances that can affect water quality: 

Bacteria such as E. coli is a key indicator of the presence of harmful bacteria and can cause illness. Treated drinking water should have no E. coli, while water for swimming should have less than 232 colony forming units (CFUs) per 100ml. 

Phosphorus is naturally occurring in bodies of water, but too much can cause excess algae growth, which reduces oxygen levels in the water and harms fish. Excess phosphorus enters streams and lakes when fertilizer is carried by stormwater runoff. 

Polychlorinated biphenyls (PCBs) are manmade chemicals used in consumer products until they were banned in 1979. These chemicals are still present in streams and can be ingested by fish. 

The map shows the polluted (red), good (green), and unassessed (purple) waterways in Central Indiana. To explore the physical, chemical, and biological factors affecting Indiana’s water quality, explore the How’s My Waterway map from EPA.

Map showing central Indiana. The map has all the waterways highlighted in either red, green, or purple to indicate which waterways are unassessed, good, or polluted. Many of the waterways are polluted with just a few that are marked as good.

Drinking Water Quality

The table shows the amount of various substances in Indianapolis's drinking water. The top substances include Fluoride, Lead, and Atrazine.
Source: Citizens Energy Group – 2019 Water Quality Report Get the data

This information is for Citizens Energy Group’s Indianapolis and Morgan County water service, which includes the blue service are shown on this map.

After treatment, drinking water had no substances that exceeded the legal limit. Substances with the highest relative amounts (compared to the limit) were fluoride, lead, and atrazine. Fluoride is added during treatment. At appropriate levels, it can prevent dental disease. Atrazine is a preemergent weed killer used frequently on lawns and corn. Lead comes from the disintegration of pipes. While the EPA sets the legal limit at 15 parts per billion, any amount over zero poses some risk.

Simple map showing Marion County and its surrounding counties.

Mosquito Counts

The bar chart shows the mosquito counts in Indianapolis from 1990 to 2020. The number of mosquitos slowly increases through the early 2010s. The numbers slowly start declining into 2020.
Source: Marion County Department of Health Get the data

Mosquitos thrive in heat and moisture and can carry West Nile Virus and other diseases. Marion County Health Department traps mosquitos at locations throughout the city to count and study them. This chart represents the number of mosquitos caught in their traps each year. Counts have been increasing since the mid-2000s.

Climate Change

By 2050 Indianapolis will receive an estimated 2.5-3.4 more inches of rain per year. There will be an average of four more extreme rain events (more than 2 inches) per year. Heavy snow days (more than 2 inches) will fall from an average of 6 now to 3 heavy snow days in 2050 and 2 heavy snow days in 2080.

Estimated increase in average temperature

The chart shows the estimated increase in average temperature for both low and high emission scenarios between 2020 and 2080. For low emission, the temperature is projected to rise by 6 degrees by 2080. For high emission, the temperature is projected to rise by 10 degrees by 2080.
Source: Purdue University

Share of precipitation that falls as snow or rain

The chart shows the estimated increase in the share of precipitation that falls as snow or rain between 2020 and 2080. Snow decreases and rain increases by just under 20 inches each by 2080.
Source: Purdue University

Number of days with high reaching over 95°

The chart shows the estimated increase in average number of days with high over 95° for both low and high emission scenarios between 2013 and 2080. For low emission, the days with high temperatures over 95° is projected to rise from 4 to 39 days by 2080. For high emission, the days with high temperatures over 95° is projected to rise from 4 to 76 days by 2080.
Source: Purdue University

Atlas Sources

Air pollution risk level is from SAVI Community Information using data from U.S. Environmental Protection Agency’s Risk Screening Environmental Index. Current climate data is from the National Weather Service. Environmental data is from U.S. Environmental Protection Agency. Climate change estimates are from Purdue University (Indiana Climate Report) and the Indiana University Environmental Resiliency Institute (Hoosier Resiliency Index).

Additional Information

Read these Encyclopedia of Indianapolis Entries for more information.