WEATHER · CLIMATE NORMALS · 1991–2020
Indianapolis Climate — Averages by Month
What the weather in Indianapolis, USaverages across a standard 30-year period. Each month's figure is the 1991–2020 mean temperature and total rainfall from the ERA5 reanalysis — the long-run normal a place settles around, not a forecast for any particular day.
Month-by-month normals
| Month | Avg temperature | Avg rainfall |
|---|---|---|
| January | -1.8 °C · coldest | 84.2 mm |
| February | 0.2 °C | 71.6 mm |
| March | 5.5 °C | 99.7 mm |
| April | 12.0 °C | 123.9 mm |
| May | 17.7 °C | 125.0 mm · wettest |
| June | 22.5 °C | 111.9 mm |
| July | 24.2 °C · warmest | 94.3 mm |
| August | 23.3 °C | 75.2 mm |
| September | 19.4 °C | 74.8 mm |
| October | 12.8 °C | 85.0 mm |
| November | 6.2 °C | 90.0 mm |
| December | 0.7 °C | 82.1 mm |
How to read these numbers
These are reanalysis normals, not readings from a single weather station. They come from the ERA5 0.25° (~25 km) global reanalysis grid, sampled at the grid cell nearest Indianapolis — centred at 39.75°N, 86.25°W. A reanalysis blends observations with a physics model onto an even grid, so a coastal or mountain city's cell can read a little cooler, warmer, wetter or drier than the city centre itself. The month-to-month shape — when it's hot, when it rains — is what these normals capture best.
“Normal” means the 1991–2020 average, the current World Meteorological Organization standard period. A normal is what a place tends toward over decades — any single day, month or year can and will depart from it.