The Climate Prediction Center’s outlook for May is dominated by uncertainty regarding both temperature and precipitation (Figure 1). The computer models could not settle on a consistent pattern for either above- or below-normal temperatures for the month and precipitation outlooks are only slightly confident that there will be above-normal precipitation in southern Indiana. Shorter-term outlooks through mid-May are predicting increasing confidence for continued below-normal temperatures but very little guidance regarding precipitation.
Figure 1. Climate outlook for May. Temperature (left); Precipitation (right). Shading indicates the probabilistic confidence for above- or below-normal conditions.
Climatologically speaking, there is less than a 10-percent chance that a hard freeze (at or below 28°F) is still likely to occur aside from the northeastern counties in Indiana (Figure 2). However, forecasts are predicting above-freezing overnight lows for this region, so the threat of any expansive, hard freeze is minimal.
Figure 2. Map showing the approximate date when climatologically there was only a 10% chance that a hard freeze would occur later.
With the recent cold temperatures, modified growing degree-day (https://www.agry.purdue.edu/ext/corn/news/timeless/HeatUnits.html) accumulations have slowed. As of April 20, 2020, GDDs are running 20 to 45 units below normal (Figure 3).
Figure 3. Average accumulated modified growing degree days since April 1, 2020.
Enjoy the warmer and drier conditions when they come. This seems like a relatively typical spring in Indiana.