Growing degree days
Heat units accumulated since planting at any location in Africa, using live weather data.
Pick the nearest town, or enter your farm's coordinates for a closer match.
Counts every full day from planting to yesterday, up to 12 months back.
Maize hybrids need roughly 1 200–1 700 GDD (°C) to physiological maturity depending on hybrid maturity class; check the seed company's figure.
Choose the planting date.
How this is calculated
Crops develop according to heat, not calendar days. Each day adds growing degree days (GDD): the day's average temperature above a base below which the crop hardly grows. Both the day's minimum and maximum are first held between the base and an upper threshold, because growth does not speed up above about 30 °C for maize.
For maize (base 10 °C, upper 30 °C), a day of 35 °C and 20 °C counts the maximum as 30: (30 + 20) ÷ 2 − 10 = 15 GDD. A day of 28 °C with a cold 5 °C night counts the minimum as 10: (28 + 10) ÷ 2 − 10 = 9 GDD. A day that never reaches 10 °C adds nothing. This is the metric form of the widely used 86/50 °F method.
The running total is compared with the GDD your cultivar needs, which seed companies publish. Maize hybrids need roughly 1 200–1 700 GDD (°C) to physiological maturity (black layer) depending on hybrid maturity class; check the seed company's figure. Weather data comes from Open-Meteo's model at the location you pick, so it can differ from a thermometer on your farm by a degree or two; your own readings are more accurate if you keep them.
Read the guide: Growing degree days explained: timing your crop by heat, not the calendar
Results are estimates for planning. Check product labels and local recommendations before you apply anything.