Growing Degree Day (GDD) Summary, May 2024

Authors: Amy Stone
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The Plant Phenology and Growing Degree Day (GDD) posts and impacts have been a Buckeye Yard and Garden onLine (BYGL) staple for years. GDD will continue to be an important part of the blog written to assist green industry professionals, Extension professionals, Extension volunteers, and people with a passion for plants and pests too.

Readers will continue to see those updates in the BYGL on a monthly basis, but there is no better way to track GDD and ultimately the plant blooms and insect activity on your own. Be sure to save this website ( ) as a favorite, and set those calendar reminders now to check the website regularly.

Here is a Growing Degree Day Refresher if GDD is new, or you need a little review!

GDD are a measurement of the growth and development of plants and insects during the growing season. Development does not occur at this time unless the temperature is above a minimum threshold value (base temperature). The base temperature varies for different organisms. It is determined through research and experimentation. The actual temperature experienced by an organism is influenced by several factors. These factors affect growth and development. For instance, depending on the weather, an organism’s temperature may be a few degrees more or less than that recorded. An organism may spend its time in the shade or under direct sunlight. The fertility and nutrient content of the soil directly affect the growth rate of plants and thereby indirectly influence insect growth rates. The presence of weeds and precipitation may indirectly influence development. Due to these factors and some other scientific considerations, a base temperature of 50 degrees Fahrenheit is considered acceptable for all plants and insects. (Source: OSU Plant Phenology Website)

The one thing that we do know is that the sequence of events – both plant and pest development – consistently occurs in the same order no matter the weather.

At the end of each month this calendar year, there will be a GDD Summary Alert Posted to BYGL. While today’s post has some areas seeing zeros – it is the start of the calendar year – we will have to see if that is true. As you can see below, 21 Ohio locations (City, County, and Zip Code) have been chosen across the state and will continue to be used for the monthly updates.

GGD Chart, ending May 31, 2024
Ohio City (County) Zip Code    GDD Unit Accumulation 
Bryan (Williams) 43506 819
Toledo (Lucas) 43615 811
Sandusky (Erie) 44870 784
Elyria (Lorain) 44035 731
Cleveland (Cuyahoga) 44120 717
Burton (Geauga) 44021 704
Jefferson (Ashtabula) 44047 690
Van Wert (Van Wert) 45891 797
Findlay (Hancock) 45840 767
Medina (Medina) 44256 694
Mt. Gilead (Morrow) 43338 755
Mt. Vernon (Knox) 43050 868
Steubenville (Jefferson) 43952 846
Dayton (Montgomery) 45417 966
Springfield (Clark) 45505 966
Columbus (Franklin) 43210 944
Lancaster (Fairfield) 43130 983
Marietta (Washington) 45750 983
Cincinnati (Hamilton) 45223 990
Hillsboro (Highland) 45133 996
Ironton (Lawrence) 45638 988

Not seeing your city or zip code? No worries! You can always check out the website, type in your Ohio zip code, and ground truth what you are seeing with what the calendar says should be occurring.

Additionally, once you are at the website, you can click on summary and it will provide you the yearly GDDs and the 20 year average. To illustrate that, I have done this with the zip code at my office (43615) in Toledo, Ohio using May 31 as the common date.


Date: May 31



GDD Unit Accumulation


2024 811
2023 579
2022 667
2021 604
2020 455
2019 504
2018 646
2017 656
2016 565
2015 612
2014 541
2013 623
2012 870
2011 520
2010 741
2009 619
2008 476
2007 681
2006 561
2005 411
2004 637

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