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Ohio State University Extension


Rapid Growing Degree Day Accumulation in May

Climate Summary

For May, temperatures averaged 2-6°F above the long-term mean (1991-2020). This led to a rapid accumulation of modified growing degree days, from 400-600 over the course of the month. This is 80-120 GDDs above the long-term mean for May (Fig 1), with seasonal totals since April 1 now sitting between 600 and 1000 (north to south). Precipitation was highly variable. Parts of west central, northeast, and southeast counties only received 1-2” (50-75% of normal). Other areas including Marion/Wyandot/Crawford Counties, across southern Ohio, and from Canton to Steubenville picked up more than 5” (125-175% of normal). According to CoCoRaHS, a site near Withamsville in Clermont County received 6.93” in May. Even where precipitation was a bit on the lighter side, frequent rainy days plagued the region early in the month, with improvements in planting windows for northwest Ohio just before Memorial Day.

Figure 1). Differences from average modified growing degree days for May 2024. The modified growing degree day calculation uses 86°F and 50°F as the maximum and minimum temperatures if conditions are warmer or cooler than those thresholds, respectively. Figure courtesy of the Midwestern Regional Climate Center (

Please visit the State Climate Office of Ohio for the latest up-to-date conditions, seasonal outlooks, and monthly climate summaries.

Figure 2). Precipitation forecast from the Weather Prediction Center for 8pm Monday June 3  – 8pm Monday June 10, 2024.

Weather Forecast

Warm, summer-like weather will start the week off, with highs generally in the 80s through Wednesday. After plenty of sunshine on Monday, clouds will start to build across the region on Tuesday with a few scattered showers and storms possible by Tuesday night. A better chance of showers and storms moves across the Buckeye State on Wednesday, followed by cooler air to end the week. Scattered showers are possible on Friday through Sunday with highs generally in the upper 60s to upper 70s across the region. The Weather Prediction Center is currently forecasting 0.50-1.00” for the bulk of the state over the next 7 days, with localized heavier amounts (Fig. 2).

 The 8-14 day outlook from the Climate Prediction Center and the 16-day Rainfall Outlook from NOAA/NWS/Ohio River Forecast Center show greater probabilities of below-average temperatures with near-normal precipitation expected (Fig. 3). Climate averages include a high-temperature range of 77-81°F, a low-temperature range of 57-61°F, and weekly total precipitation of 0.90-1.20”.

Figure 3) Climate Prediction Center 8-14 Day Outlook valid for June 11 - 17, 2024, for left) temperatures and right) precipitation. Colors represent the probability of below, normal, or above normal conditions.

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.