Products Developed as Part of the Maize Trust Early Warning For Farmers Project
31 grain towns in the summer-grain region · next 3 days · init 2026-10-07 14:00 SAST (2026-10-07 12:00 UTC) (20261007_12z). Tap a town for its full forecast. model soil state carried forward from cycle 20261006_12z.
Rain per 08:00-08:00 gauge day at the town, with the range within ~15 km beneath (showers are hit-and-miss). Planting rain is likely with 25 mm or more here, possible nearby when under 25 mm here but 25 mm or more within ~15 km. The small line under the total compares it with the previous run.
Good spray hours (Delta-T 2-8, wind 3-15 km/h, no rain within 2 h) between 05:00 and 19:00, and field access hours between 06:00 and 18:00 when the model topsoil is under 90 % of field capacity and it isn't raining. One number per day.
Crop water use for maize at mid-season over all forecast days (FAO-56), with the irrigation still needed after effective rain beneath; set your own crop, stage and pivot on the town page. Lowest night and highest day temperature.
Worst level over the forecast (amber, red; hover for when). FROST 5 °C or lower in calm clear air (red 2 °C), HEAT 30 °C+ (red 35 °C), THI livestock heat 68+ (red 79), HOT SOIL surface 50 °C+ (red 60 °C), WIND 30 km/h sustained or 40 km/h gusts (red 60 km/h gusts), DOWNPOUR 15 mm/h+ (red 30 mm/h), COLD&WET rain under 15 °C (red: also windy 20 km/h+) -- newborn calves, lambs, shorn sheep. Disease weather: GLS grey leaf spot and NCLB northern corn leaf blight (maize), RUST soybean rust, SCLERO Sclerotinia (soybeans, sunflowers). A town's page also flags multi-day heat/wind/cloud spells and potato lifting frost, which don't fit a single-hour badge.
Every column.
| Town | Thu 08 Oct | Fri 09 Oct | Total | Planting rain | Good spray hours per day |
Field access hours per day |
Maize water use mid-season | Min / max °C | Watch | Disease weather |
|---|---|---|---|---|---|---|---|---|---|---|
| Free State | ||||||||||
| Bothaville (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 0 · 2 | 12 · 12 | 19 mmirrigate 19 mm | 16 / 33 | HEATTHI | – |
| Hoopstad (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 3 · 3 | 12 · 12 | 18 mmirrigate 18 mm | 15 / 33 | HEATTHI | – |
| Wesselsbron (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 4 | 12 · 12 | 18 mmirrigate 18 mm | 14 / 33 | HEATTHI | – |
| Bultfontein (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 4 | 12 · 12 | 18 mmirrigate 18 mm | 13 / 32 | HEATTHI | – |
| Viljoenskroon (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 1 · 3 | 12 · 12 | 17 mmirrigate 17 mm | 15 / 31 | HEATTHI | – |
| Kroonstad (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 1 · 1 | 12 · 12 | 18 mmirrigate 18 mm | 16 / 32 | HEATTHI | – |
| Lindley (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 3 · 0 | 12 · 12 | 17 mmirrigate 17 mm | 13 / 30 | HEATTHI | – |
| Heilbron (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 1 | 12 · 12 | 16 mmirrigate 16 mm | 13 / 29 | THI | – |
| Frankfort (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 1 · 2 | 12 · 12 | 16 mmirrigate 16 mm | 13 / 30 | HEATTHI | – |
| Tweeling (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 4 · 4 | 12 · 12 | 16 mmirrigate 16 mm | 13 / 30 | HEATTHIWIND | – |
| Reitz (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 2 | 12 · 12 | 16 mmirrigate 16 mm | 12 / 29 | THIWIND | – |
| Petrus Steyn (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 3 · 1 | 12 · 12 | 16 mmirrigate 16 mm | 12 / 29 | THIWIND | – |
| Bethlehem (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 3 · 2 | 12 · 12 | 15 mmirrigate 15 mm | 12 / 29 | THI | – |
| Vrede (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 3 · 2 | 12 · 12 | 16 mmirrigate 16 mm | 12 / 29 | THI | – |
| Petrusburg (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 3 · 1 | 12 · 12 | 18 mmirrigate 18 mm | 14 / 32 | HEATTHI | – |
| North West | ||||||||||
| Lichtenburg (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 0 · 0 | 12 · 12 | 17 mmirrigate 17 mm | 17 / 30 | HEATTHIWIND | – |
| Coligny (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 1 | 12 · 12 | 17 mmirrigate 17 mm | 14 / 30 | HEATTHIWIND | – |
| Ventersdorp (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 0 · 1 | 12 · 12 | 16 mmirrigate 16 mm | 15 / 29 | HEATTHIWIND | – |
| Potchefstroom (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 1 | 12 · 12 | 18 mmirrigate 18 mm | 18 / 31 | HEATTHI | – |
| Klerksdorp (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 1 | 12 · 12 | 16 mmirrigate 16 mm | 19 / 31 | HEATTHIWIND | – |
| Ottosdal (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 3 · 1 | 12 · 12 | 16 mmirrigate 16 mm | 13 / 30 | HEATTHIWIND | – |
| Delareyville (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 0 · 1 | 12 · 12 | 17 mmirrigate 17 mm | 13 / 32 | HEATTHIWIND | – |
| Schweizer-Reneke (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 3 · 1 | 12 · 12 | 17 mmirrigate 17 mm | 14 / 32 | HEATTHIWIND | – |
| Wolmaransstad (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 0 · 2 | 12 · 12 | 18 mmirrigate 18 mm | 16 / 32 | HEATTHIWIND | – |
| Christiana (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 2 | 12 · 12 | 19 mmirrigate 19 mm | 15 / 34 | HEATTHI | – |
| Vryburg (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 1 · 0 | 12 · 12 | 18 mmirrigate 18 mm | 19 / 34 | HEATTHI | – |
| Mpumalanga | ||||||||||
| Delmas (3 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 3 | 12 · 12 | 16 mmirrigate 16 mm | 14 / 29 | THI | – |
| Bethal (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 3 · 4 | 12 · 12 | 16 mmirrigate 16 mm | 12 / 30 | THI | – |
| Standerton (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 4 | 12 · 12 | 16 mmirrigate 16 mm | 13 / 30 | THI | – |
| Ermelo (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 2 · 2 | 12 · 12 | 16 mmirrigate 16 mm | 11 / 29 | THI | – |
| Belfast / Dalmanutha (9 km) | 0 | 0 | 0≈ prev. 0 | No planting rain | 1 · 1 | 12 · 12 | 15 mmirrigate 15 mm | 12 / 28 | THI | – |
Towns inside the 3 km nest (North West, Gauteng and the northern Free State) use it; the rest use the 9 km domain. Rain days run 08:00 to 08:00 SAST, the way rain gauges are read.
| 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 |