INDIANAPOLIS — The old saying "don't plant until after Mother's Day" has proven to be true this year. Low temperatures the next three nights will drop into the mid 30s, if not colder in some places.
The average date of the last 36° (when frost can occur) or colder temperature in Indianapolis since 1871 is April 29 and May 31, 1889, is the latest.
You'll want to bring in tender plants and/or cover them up the next three nights with Wednesday bringing the greatest odds of a widespread frost due to the positioning of a high-pressure system over central Indiana.
That brings a clear sky and light to calm wind that maximizes radiational cooling.