Farm Tools
Agricultural decision support from live weather data
Spray Conditions
Delta-T: 3.9°CRecent rain (0.1 mm last hour) — foliage may be wet
Traditional (Boom/Rig) ✓ Good
Delta-T: 3.9°C · Wind: 8 km/h · RH: 69%
Drone ✓ Good
Delta-T: 3.9°C · Wind: 8 km/h · RH: 69%
What is Delta-T?
Delta-T is the difference between the air temperature and the wet-bulb temperature. It's the single best indicator of spray conditions because it captures both temperature and humidity in one number.
Below 2 °C — Inversion likely. Spray hangs and drifts. Do not spray.
2–8 °C — Ideal for traditional spraying.
2–10 °C — Acceptable for drone spraying.
Above 8 °C — Rapid evaporation risk.
Traditional (ground rig/boom)
Wind 3–15 km/h — Below 3 signals inversion; above 15 causes off-target drift.
Temperature 10–28 °C — Cold reduces plant uptake; heat increases evaporation.
Humidity 40–90% — Below 40% droplets evaporate before reaching the target.
Delta-T 2–8 °C — Below 2 indicates inversion; above 8 means rapid evaporation.
Drone (UAV spraying)
Wind up to 25 km/h — Closer to canopy so drift is less of a factor.
Humidity down to 35% — Shorter nozzle-to-target distance means less evaporation.
Delta-T up to 10 °C — Less droplet travel time allows wider tolerance.
Additional checks
Active rain — Rain washes off recently applied spray. Wait for rain to stop and foliage to dry.
Recent rain — Wet leaves dilute spray application and reduce effectiveness.
Inversion risk — Calm winds after sunset with low Delta-T. Spray particles suspend and drift kilometres. One of the most dangerous conditions for off-target damage.
Based on SA agricultural best practice. Always check product labels for specific requirements.
Fire Danger Index
FDI 0 — LowLow fire danger — safe for controlled burns with precautions.
McArthur Grassland FDI (Mark 5) adapted for Free State conditions. Grass curing estimated seasonally. Higher index during dry winter months.
Frost Risk Tonight
LowRisk score: 0/100
Frost unlikely tonight — no action needed.
Based on temperature, humidity, wind, and dew point. Most accurate from mid-afternoon onward. Frost season: April–October.
Fog Risk
LowRisk score: 0/100
Dew depression: 5.9°C
Type: Radiation fog
Air too dry for fog (69%)
Light wind — may limit fog
Fog season (Apr–Aug)
Fog unlikely — good visibility expected.
Radiation fog unlikely with current conditions. Dew point depression is 5.9°C. Solar heating makes fog unlikely during the day.
Based on dew point depression, humidity, wind speed, time of day, and season. Radiation fog is most common in the region — forms on clear, calm nights.
Evapotranspiration (ETo)
2.2 mm/day — ModerateNormal water demand — irrigate on schedule
Maize (mid-season)
2.6 mm/day
Kc = 1.2
Wheat (mid-season)
2.5 mm/day
Kc = 1.15
Pasture
2.2 mm/day
Kc = 1.0
Crop water need ≈ ETo × crop coefficient (Kc). Values shown are mid-season peaks. Method: penman-monteith (estimated). Based on FAO-56 guidelines.
Livestock Conditions
THI 67
No heat stress — cattle are comfortable.
Normal feeding, production, and behaviour expected.
20.4°C
Effective temperature
No cold stress — cattle are comfortable.
High water demand — ensure troughs are full and pumps running. Consider additional water points.
Temperature-Humidity Index (THI) — cattle stress thresholds: 68 mild, 72 moderate, 80 severe, 90 emergency
THI based on NRC (1971) formula. Cold stress accounts for wind chill and wet coat conditions. Water demand estimates for SA cattle breeds at stated body weight. Calving season: Jul–Sep.
THI 67
No heat stress — sheep are comfortable.
Normal grazing, feed intake and behaviour expected.
20.4°C
Effective temperature — shearing season
No cold stress — sheep are comfortable. Monitor recently shorn sheep.
Shearing season — recently shorn sheep are 3× more vulnerable to cold
Water intake rising — check trough levels more frequently.
Temperature-Humidity Index (THI) — sheep stress thresholds: 70 mild, 76 moderate, 82 severe, 87 emergency
Sheep THI thresholds adjusted for small ruminants. Cold stress uses shearing-season awareness (Apr–May, Aug–Sep) — shorn sheep lose 3× body heat. Common Eastern FS breeds: Dohne Merino, SAMM, Merino, Afrino, Dorper, Damara. Water demand for 60 kg ewe. Lambing season: Jul–Oct.
Chill Units
Very Low Season complete — 20250
Chill Units (Utah)
May 1 – Aug 31
0
Days Recorded
May – Aug 2025
200
CU to Next Milestone
Low-chill peaches & nectarines
Variety Milestones
Very few chill units accumulated. Season may not have started or conditions are too warm.
Utah chill model — estimates hourly temps from daily min/max using sine interpolation. Season: May 1 – Aug 31. Weights: 2.5–9.1°C = 1 CU/hr (optimal), >16°C negates chill.
Rainfall Tracker
Well Below Oct 2025 – Mar 2026255
mm this season
600
mm regional average
Full season (Oct–Mar)
43%
of seasonal average
Season complete
Monthly Breakdown
Rainfall well below seasonal average — drought conditions likely. Consider irrigation planning and water conservation.
Rain season: Oct 1 – Mar 31. Regional average: 600 mm/season. Data from DailySummary rain totals.
Farm Tools provide general guidance only — not professional advice. Weather data may be delayed or inaccurate. Always apply your own judgement. Full disclaimer.