2026 Plant Phenology and Growing Degree Day Calendar
By Amy Stone Ashley Kulhanek
January 4, 2026
As temperatures warm, we will begin accumulating growing degree day (GDD) units. You will see those updates in the BYGL, 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 ( https://weather.cfaes.osu.edu/gdd/default.asp ) 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 insects and plants. 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)
While today's post has everyone seeing zeros - it is the start of the calendar year. As you can see below, 20 Ohio locations (City, County, and Zip Code) have been chosen across the state and will continue to be used for the updates, and linked to future BYGL Alerts.
GGD Chart, January 2, 2026
Ohio City (County)Zip Code GDD Unit Accumulation
Bryan (Williams)
43506
0
Toledo (Lucas)
43615
0
Sandusky (Erie)
44870
0
Elyria (Lorain)
44035
0
Burton (Geauga)
44021
0
Jefferson (Ashtabula)
44047
0
Van Wert (Van Wert)
45891
0
Findlay (Hancock)
45840
0
Medina (Medina)
44256
0
Mt. Gilead (Morrow)
43338
0
Mt. Vernon (Knox)
43050
0
Steubenville (Jefferson)
43952
0
Dayton (Montgomery)
45417
0
Springfield (Clark)
45505
0
Columbus (Franklin)
43210
0
Lancaster (Fairfield)
43130
0
Marietta (Washington)
45750
0
Cincinnati (Hamilton)
45223
0
Hillsboro (Highland)
45133
0
Ironton (Lawrence)
45638
0
Not seeing your city or zip code? No worries! You can always check out the website and type in your Ohio zip code.
It is a good reminder that sometimes we have microclimates or for other various reasons the numbers just don't match up to what you experiencing locally. But becoming familiar with the sequence or order is a valuable tool - that plant and insect activity is always the same.
We wish you the best in 2026 and be sure to include monitoring growing degree days and plant phenology throughout the new year!
Tags
More Information
The Ohio State Phenology Calendar