This spring is likely to be more of a tale of individual months than of a season. For the three-month period of March, April and May, the national Climate Prediction Center (CPC) predicts Indiana to be warmer and wetter than the climatological average conditions. For temperatures, the signal is stronger for warmth in Northern Indiana than in Southern Indiana. For precipitation, the wet signature is stronger in Southern Indiana than in Northern Indiana. However, much of this signal depends on the setup in March.
El Nino is on its way out, to be replaced by the El Nino-Southern Oscillation’s (ENSO’s) Neutral phase (as opposed to the La Nina or El Nino phases) by the end of the spring. While El Nino subsides, the precipitation signature for March has equal chances of above, average or below normal precipitation, setting the stage for slightly wetter signals in April and May. This is consistent with the trend of narrow planting windows in the spring in Indiana. At the earliest, ENSO Neutral conditions begin in April, which removes one relatively strong predictor (El Nino) from the forecast. Trends over the past 30 years toward increasing precipitation are generally stronger in Southern Indiana than Northern Indiana. The CPC map reflects this trend.
Meanwhile, temperature signals trend more toward long-term historical trends than anything related to ENSO. Northern conditions trend warmer in the nation, with Indiana following suit. However, the trend for warmer temperatures should not be taken as a sign to start unseasonable activities. The likelihood for a normal period of frost and/or freezing temperatures remains high throughout the month of March. For further guidance on the climatology of the last spring freeze and frost dates, check out the Midwestern Regional Climate Center’s Freeze Date Tool.
“It’s important to assess the climatological risk associated with early planting and potential late season freeze events,” according to Beth Hall, Indiana State Climatologist. “While every spring is different, tools such as the Freeze Date Tool can quickly provide guidance that help farmers and gardeners make more informed decisions.”
Many pest cycles depend on growing degree days in the air or soil with different base temperatures. The recent late February warmth, if sustained, could mean some insects emerge early. Likewise, early flowering plants could show color earlier than expected. However, the likelihood of a freeze event is high, so the need to ensure sensitive desirable plants are protected may be greater this year than in some years past. Don’t forget Bradford or Callery Pears are not a desirable plant. For more information, please contact the Indiana State Climate Office at 765-494-8060 or hschmitz@purdue.edu.