INDIANAPOLIS – We have been stuck in a La Niña pattern for a while now, and, according to the National Weather Service’s latest forecast, La Niña will continue into the fall. How will this impact our fall weather here in Indiana?

What is La Niña?

La Niña refers to the periodic cooling of ocean surface temperatures in the central and east-central equatorial Pacific. This typically occurs every 3 to 5 years or so and represents a cool phase of the El Niño/Southern Oscillation (ENSO) cycle. During a La Niña event, the changes in Pacific Ocean temperatures affect the patterns of tropical rainfall from Indonesia to the west coast of South America.  These changes in tropical rainfall patterns affect weather patterns throughout the world.

La Niña impacting fall in Indiana

La Niña can mean drier-than-normal conditions across a lot of the country. The newest outlook for September through November does show a drier-than-normal forecast for us here in Indiana.

In terms of temperatures, most of the state is forecasted to see slightly above-average temperatures during the fall season.

These dry and warmer-than-average temperatures would not be good for drought conditions across the state and would impact our fall foliage too.

How La Niña could impact fall foliage

In order to reach peak fall foliage, we need a few ingredients:  

  • Chilly nights 
  • Mild, sunny days 
  • No big storms 
  • First light frost 

The precipitation forecast favors less rain than average, which is good news for the fall foliage. The temperature forecast is not good news for fall foliage, however. If Indiana does not see a normal first frost or chilly nights, that could slow down the fall foliage process.

Typically, our first light frost varies from the end of September to the end of October, depending on which part of the state you are in. 

After November, the probability of La Niña continues to drop. NOAA forecasters caution that’s a long way out, and so the forecast is less reliable. If La Niña does end in the winter months, we would then end an ENSO-neutral pattern.