The Weather Project · Crop development & thermal time
Growing degree day forecasts for Australian crops
See the thermal time forecast to accumulate each day. Compare crop profiles and regional patterns to support crop-development monitoring and scheduling.
Understand the product
What are growing degree days?
Growing degree days express thermal accumulation above a selected base temperature, in degree-days (°C·day). In these products, positive temperature excess is weighted by the model timestep across the local calendar day. Temperatures below the base contribute zero.
Choose a compatible crop profile
The available profiles use 10°C for wine grapes, 4.4°C for wheat/barley and 10°C for maize/cotton. These are configured reference profiles, not a claim that every variety or stage shares the same response. Maize/cotton and wine grapes use the same base here, so their maps can match.
Daily thermal time is not a season total
Each map shows one local day’s forecast contribution, rather than accumulation from sowing, budburst or another seasonal starting point. To use a development target, maintain an observed accumulation with a consistent start date and compatible calculation method, then treat the forecast as the outlook ahead.
Use alongside crop observations
GDD can help anticipate faster or slower thermal development and prioritise field checks. Variety, water stress, photoperiod and extreme temperatures can alter crop response. The maps do not predict an exact flowering or harvest date, and this thermal-time product is not a heat-stress measure.
See what the maps look like
Examples illustrate the format and legend. They are not a live forecast briefing; use the forecast viewer for the latest available run and valid time. Select an image to open it at full size.
From the map to your site
Open the forecast viewer, choose your region and product, then read the model run and local valid date. Compare related maps over matching periods and check local observations before making a time-sensitive decision. Longer-range forecasts are best used for planning and reassessed as the date approaches.
Common questions
Can I compare all three profiles directly?
Compare maps using the same base and method when assessing thermal time. A lower base counts more temperature exposure, so the wheat/barley profile will generally accumulate more than a 10°C profile under the same conditions.
Where is maize/cotton?
Open the agricultural viewer and choose GDD · maize / cotton. Select the local forecast date, then read the base and units printed on the map.
Independent model guidance from The Weather Project. Check the map’s method, coverage and valid period. Regional guidance complements local measurements and crop-specific advice.