Story County, Iowa / Corn
Total GDD:
3151
(Oct 15)
Day 168 / 168 (100%)
Current Season
Total GDD:
3151
(Oct 15)
Method: 50°F
7-Day Daily Avg: 9.5
7-Day Projection: 3217 by Oct 22
Season: May 01, 25 - Oct 15, 2025
Key Freeze Dates (32°F)
Last Freeze:
10%: 04-11
50%: 04-24
90%: 05-06
10%: 04-11
50%: 04-24
90%: 05-06
First Freeze:
10%: 09-22
50%: 10-10
90%: 10-17
10%: 09-22
50%: 10-10
90%: 10-17
Growing Degree Days (GDD) track heat accumulation to predict when plants reach growth stages, pests emerge, and diseases become active.
Thresholds mark specific GDD values when events typically occur, with crossing dates showing when your season reaches each milestone.
Thresholds & Notes
VE - Emergence
120
°D
May 12, 2025
|
May 12, 2024
|
May 10, 2023
|
May 11, 2022
Growth Stage
Coleoptile breaks surface
V2 - Two Leaf
200
°D
May 16, 2025
|
May 17, 2024
|
May 14, 2023
|
May 15, 2022
Growth Stage
Two collared leaves
V6 - Six Leaf
475
°D
Jun 9, 2025
|
Jun 3, 2024
|
May 31, 2023
|
Jun 4, 2022
Growth Stage
Growing point above ground, nodal roots active
V10 - Ten Leaf
815
°D
Jun 23, 2025
|
Jun 18, 2024
|
Jun 17, 2023
|
Jun 19, 2022
Growth Stage
Ear shoots developing
V14 - Fourteen Leaf
1135
°D
Jul 5, 2025
|
Jun 30, 2024
|
Jun 30, 2023
|
Jul 1, 2022
Growth Stage
Tassel forming, ear size determined
VT - Tasseling
1350
°D
Jul 14, 2025
|
Jul 11, 2024
|
Jul 10, 2023
|
Jul 9, 2022
Growth Stage
Tassel fully emerged, pollen shed begins
R1 - Silking
1450
°D
Jul 19, 2025
|
Jul 14, 2024
|
Jul 15, 2023
|
Jul 13, 2022
Growth Stage
Silks visible, pollination critical
R3 - Milk Stage
1925
°D
Aug 7, 2025
|
Aug 3, 2024
|
Aug 3, 2023
|
Aug 1, 2022
Growth Stage
Kernels yellow, milky fluid
R5 - Dent Stage
2450
°D
Sep 1, 2025
|
Aug 27, 2024
|
Aug 25, 2023
|
Aug 25, 2022
Growth Stage
Dent forming, 55% moisture
R6 - Black Layer
2700
°D
Sep 16, 2025
|
Sep 11, 2024
|
Sep 5, 2023
|
Sep 4, 2022
Growth Stage
Physiological maturity, 30-35% moisture