08 Oct
06:00
Products Developed as Part of the Maize Trust Early Warning For Farmers Project
Free State · WRF 3 km · init 2026-10-07 14:00 SAST (2026-10-07 12:00 UTC) (20261007_12z) · times SAST · all towns · live radar (last hour)
No planting rain not in the next 3 days
Whole forecast: 0 mm here, 0–0 mm within ~15 km. Within 48 h: 0 mm (up to 0 mm within ~15 km). Up to Fri 14:00 SAST this run gives 0 mm, about the same as the previous run (20261006_12z: 0 mm for the same hours). Also: soil warm enough (20 °C or more at 08:00); soil at or above 10 °C for 2 mornings running (2 at the stricter 13 °C some farmers use).
topsoil moisture at the start of this forecast: 42% of field capacity · model soil state carried forward from cycle 20261006_12z.
Next workable spell: Thu 06:00–17:00 (12 h, dry crop, land should carry a combine or planter); conditions are workable now. No rain is forecast in this window.
Workable: daytime (06:00-18:00 SAST), no rain falling, RH under 80 %, and the model topsoil below field capacity (can carry machinery). A regional guide, not a reading of your own land.
| Thu 08 Oct | Fri 09 Oct | |
|---|---|---|
| Rain (mm) · range ~15 km | 0 | 0 |
| Max °C (day) | 30 | 32 |
| Min °C (following night) | 19 | 16 |
| Soil 0-10 cm at 08:00 (°C) | 20 | 23 |
| Soil 0-10 cm at 10:00 (°C) | 27 | 30 |
| Good spray hours (05-19 h) | 1 | 1 |
| Heat units (maize, °C·d) | 14 | 15 |
| Heat above 30 °C (°C·d) | 0.0 | 0.4 |
| Sunshine (MJ/m²) | 29 | 29 |
| Evaporative demand ET₀ (mm) | 7.4 | 7.7 |
| Strongest gust (km/h) | 20 | 25 |
| Leaf-wetness hours | 0 | 0 |
| Field access hours (06-18 h) | 12 | 12 |
| Highest livestock THI | 73 | 75 |
Crop water use = crop coefficient (FAO-56 Table 12) × reference evapotranspiration ET₀ from the forecast. Effective rain counts 80 % of daily rain of 5 mm or more. Pivot hours assume the capacity is the gross daily application and losses are set by the efficiency. Days marked * are partial.
Whether the weather allows infection: the longest spell of leaf wetness (estimated as relative humidity 90 % or more, or rain) at temperatures the disease needs. Risk also needs a susceptible growth stage and the disease to be present, e.g. maize on maize residue for grey leaf spot.
| Thu 08 Oct | Fri 09 Oct | |
|---|---|---|
| Grey leaf spot Maize · 11 h+ leaf wetness at 22-30 °C (Ward et al. 1999) | Low no qualifying wet spell | Low no qualifying wet spell |
| Northern corn leaf blight Maize · 6-18 h dew at 18-27 °C (Levy & Cohen 1983) | Low no qualifying wet spell | Low no qualifying wet spell |
| Soybean rust Soybeans · 6 h minimum, 10-12 h near optimum at 15-28 °C (Melching et al. 1989) | Low no qualifying wet spell | Low no qualifying wet spell |
| Sclerotinia (white mould, head rot) Soybeans, sunflowers · Working rule: 12 h+ wet at 15-25 °C in a day; two such days in a row = high | Low no qualifying wet spell | Low no qualifying wet spell |
Delta-T 2-8, wind 3-15 km/h, no rain now or in the next 2 h, not in calm air after dark
Modelled 0-10 cm soil temperature: maize germination needs 10 °C, emergence is slow below about 12 °C; groundnuts need about 18 °C
Model topsoil (0-10 cm) moisture against field capacity for the local soil type: under 90 % accessible, 90-100 % soft (rutting, compaction), at or above field capacity or raining too wet for machinery
Crop wet from rain now, 5 mm+ in the last 12 h, or dew / humid air (RH 90 %+)
Pivot and sprinkler losses to wind drift and evaporation: higher with wind over 15 km/h or dry daytime air (RH under 25 %), high with wind over 25 km/h; lower at night
Temperature-humidity index for cattle: 68+ alert (dairy cattle start losing production), 79+ danger
2 m temperature: yield losses build up above 30 °C; above 35 °C pollen viability falls (critical at tasselling)
Model skin temperature: 50 °C+ stresses emerging seedlings, 60 °C+ scorches them and cooks tubers
Screen (2 m) temperature, not canopy temperature: 5 °C or lower in calm, clear air (ground frost), 2 °C or lower = frost likely
Sustained 30 km/h+ blasts sand over seedlings on dry sandy lands; gusts 60 km/h+ flatten wet crops
Hourly rain above ~15 mm/h exceeds typical infiltration (erosion, crusting, runoff)
Rain with a cool daytime temperature (under 15 °C): the combination newborn calves, lambs and freshly-shorn sheep struggle with, worse again with wind
| Product | Threshold | Basis |
|---|---|---|
| Spray conditions | Delta-T 2-8 °C good, 8-10 marginal, over 10 unsuitable; wind 3-15 km/h good, over 20 km/h unsuitable; no rain within 2 h | GRDC, Weather essentials for pesticide application; product labels (rainfast times of 1-6 h) |
| Planting rain | 25 mm likely, 15-20 mm plantable if soil is already moist, 10-15 mm some (not planting) rain, 5-10 mm false-start risk | 25 mm: onset of maize planting rains, Tadross, Hewitson & Usman (2005), J. Climate 18. The lower bands are interviewee-quoted working values (26 maize-triangle farmers, Apr-Jul 2025), not a published standard. |
| Soil temperature | 10 °C maize germination base (13 °C alternative some farmers use); emergence slow below about 12 °C; 18 °C for groundnuts; checked at 08:00 and 10:00 SAST | Maize and groundnut production guidelines (e.g. Nielsen, Purdue University); 13 °C and the 10:00 reading are interviewee-quoted working values |
| Heavy clay pre-rain planting | 30 mm within 48 h on clay/clay-loam/silty-clay soil (Noah STAS classes 9-12) | Working value from two interviewees who plant heavy turf soils ahead of a sure heavy rain, because the lands cannot be entered once wet |
| Heat/wind/cloud spells | 2+ days at 33 °C+ (flowering heat), 2+ days at 40 °C+ (potato irrigation lead), 3+ days sustained wind 30 km/h+ (seedling sandblasting), 2+ days under 15 MJ/m² sunshine (potato bulking) | Interviewee-quoted working values -- duration, not a single extreme hour, was what farmers described as doing the damage |
| Livestock cold & wet | Rain with 2 m temperature under 15 °C (worse with wind 20 km/h+) | Working value: newborn calves, lambs and freshly-shorn sheep are vulnerable to cold combined with wet, per interviewees; THI (above) covers heat stress only |
| Potato lifting frost | Morning minimum -3 °C or lower | Interviewee-quoted working value (tuber cracking at lifting) |
| Harvest window | Workable = daytime (06:00-18:00 SAST), no rain falling, RH under 80 %, topsoil below field capacity | Working definition built from interview descriptions of what stops a combine (F03, F06, F20, F21); not a calibrated grain-moisture or machine-specific model |
| Model soil state | Topsoil moisture at the start of this forecast, and whether it carried forward from the previous cycle's own simulated state or started fresh from GFS | lib/soil_warm_start.py cycles soil moisture/temperature between runs (not a full atmospheric warm start); reset to a fresh GFS-derived start every Sunday UTC to stop drift accumulating |
| Crop heat | 30 °C (yield losses per degree-day above 30 °C), 35 °C (pollen viability) | Lobell et al. (2011), Nature Climate Change 1; Hatfield & Prueger (2015), Weather and Climate Extremes 10 |
| Heat units | Base 10 °C, cap 30 °C, hourly method | McMaster & Wilhelm (1997), Agric. For. Meteorol. 87 |
| Frost | 2 m temperature 2 °C or lower on calm, clear nights (5 °C possible) | Snyder & de Melo-Abreu (2005), Frost Protection, FAO |
| Evaporative demand | FAO-56 Penman-Monteith reference ET₀ | Allen et al. (1998), FAO Irrigation and Drainage Paper 56 |
| Hot soil surface | 50 / 60 °C model skin temperature | Working value |
| Wind damage | Sustained 30 km/h, gusts 40 / 60 km/h | Working value |
| Downpours | 15 / 30 mm per hour | Working value |
| Crop water use | ETc = Kc × ET₀; Kc (initial / mid / end): maize 0.30 / 1.20 / 0.60, soybeans 0.40 / 1.15 / 0.50, sunflowers 0.35 / 1.10 / 0.35 | Allen et al. (1998), FAO-56, Table 12 |
| Effective rain | Daily rain under 5 mm ignored, 80 % of the rest | FAO fixed-percentage method (working values) |
| Irrigation losses | Wind over 15 km/h or daytime RH under 25 %: higher; wind over 25 km/h: high | Playán et al. (2005), Agric. Water Manage. 76 (trend); limits are working values |
| Field access | Model topsoil (0-10 cm) moisture under 90 % of field capacity: accessible; 90-100 %: soft (rutting, compaction); at or above field capacity, or raining: too wet | Earl (1997), Soil & Tillage Research 40; field capacity per soil class from the Noah land-surface model (REFSMC) |
| Livestock heat (THI) | Temperature-humidity index 68+ alert, 79+ danger (same as the impact dashboard) | THI formula NRC (1971); 68 for dairy cattle (Zimbelman et al. 2009); 79 danger (Livestock Weather Safety Index) |
| Leaf wetness | Relative humidity 90 % or more, or rain | Sentelhas et al. (2008), Agric. For. Meteorol. 148 |
| Grey leaf spot | 11 h+ leaf wetness at 22-30 °C | Ward et al. 1999 |
| Northern corn leaf blight | 6-18 h dew at 18-27 °C | Levy & Cohen 1983 |
| Soybean rust | 6 h minimum, 10-12 h near optimum at 15-28 °C | Melching et al. 1989 |
| Sclerotinia (white mould, head rot) | Working rule: 12 h+ wet at 15-25 °C in a day; two such days in a row = high | Working rule |