Hazard Alerts & Crop Phase Thresholds
This article explains how the platform determines when weather conditions become a concern - covering the four weather hazards, how growth phases work, and the thresholds applied to each crop and phase combination.
The four weather hazards
The platform monitors four types of weather stress for each crop.
Heat stress is tracked using daily maximum temperature (Tmax). High temperatures during reproductive phases cause pollen sterility, accelerated ripening, and yield reduction. The impact is greatest during flowering and grain filling, when the developing grain or fruit is most vulnerable.
Low temperature and frost is tracked using daily minimum temperature (Tmin). Frost is particularly damaging when it occurs after a crop has broken dormancy, because tissues that were cold-hardened are no longer protected. A single hard frost during flowering can eliminate a season's crop. The platform accounts for this by applying the tightest thresholds during post-dormancy sensitive phases.
Drought is tracked using root-zone soil moisture (RZSM) relative to the historical distribution for each location and phase. Soil moisture is used rather than raw precipitation because it integrates all the factors a plant actually experiences - rainfall, evaporation, soil properties, and antecedent conditions. The drought signal is expressed as a percentile: how dry is the root zone compared to the same period historically?
Excessive Rainfall is tracked using accumulated precipitation over a rolling window. Waterlogging causes root oxygen stress, degrades soil structure, promotes fungal disease, and can delay or prevent field operations such as planting and harvest.
Warning and Critical thresholds
For each hazard, each crop, and each growth phase, the platform defines two threshold levels.
A Warning alert is generated when conditions are approaching stress levels - an early indicator that production risk may be developing. A Critical alert is generated when conditions are causing significant crop stress with a high likelihood of yield reduction or quality loss.
One alert can be generated per hazard per day per location. The classification (Warning or Critical) depends on how far conditions have crossed the relevant threshold. Alerts accumulate across the season as a weighted count - Critical alerts contribute 2 points, Warning alerts contribute 1 - so a season with more severe stress accumulates a higher total faster than one with marginal exceedances.
Why thresholds vary by growth phase
The same weather condition can have very different consequences depending on when it occurs in the crop cycle. A soil moisture deficit that is perfectly normal during harvest can be damaging during flowering, and catastrophic during a sensitive reproductive window.
For this reason, each crop's growing season is divided into growth phases, and separate thresholds are defined for each phase based on the crop's agronomic sensitivity at that stage. Phases with higher weather sensitivity - typically flowering, fruit set, and grain filling - have tighter thresholds, meaning the same weather condition triggers alerts more readily. Phases where some stress is normal or even beneficial - such as harvest or dormancy - have relaxed thresholds.
For temperature-based hazards, thresholds are fixed values in °C that vary by phase. For example, a daily maximum temperature above 32°C triggers a Critical heat stress alert for wheat during flowering - because pollen sterility sets in above that level. During dormancy, the same temperature would not register at all, since the crop is cold-hardened and heat is not a meaningful risk. Similarly, a minimum temperature just below 0°C triggers a Critical frost alert during bilberry flowering, when the newly emerged blossoms are highly sensitive, but only a Warning during the hardening phase in autumn, when the plant is building cold tolerance.
For drought specifically, thresholds are expressed as percentiles of the historical soil moisture distribution for that location and phase. This makes the signal self-normalising: it adjusts automatically for regional climate differences, soil types, and seasonal patterns. A "Warning" threshold of the 20th percentile means the root zone is drier than it has been in 80% of historical seasons at the same point in the crop cycle - regardless of what the absolute moisture value is.
The specific growth phases and thresholds for each crop are visible within the platform. Expanding the crop season progress bar on the dashboard opens the Crop Profile, which shows the full phase calendar and the main weather risks associated with each phase.