FAQ — FarmWeather.co.za

FarmWeather is a free, independent weather platform built for the farming community around Reitz in the Free State. It collects hyper-local weather data from stations spread across the area and displays it in one place — so you can see what's happening on your farm and on your neighbours' farms.

Unlike national weather services that report on large regions, FarmWeather focuses on farm-level accuracy. A thunderstorm can drop 30 mm on one farm and nothing 5 km away — this platform captures that difference.

Farmers register on the site and add their weather stations. Each station gets a unique webhook URL. The station hardware (or you, manually) sends readings to that URL, and FarmWeather stores, processes, and displays the data.

Three types of stations are supported:

Ecowitt Native — Ecowitt hardware sends data directly via HTTP POST. Recommended for Ecowitt owners.
Weather Underground (WU) Protocol — A widely-supported format. Works with Ecowitt, Davis, Ambient Weather, and many others.
Manual — No hardware needed. Record readings via the web form or by sending an email.

Data is displayed on your personal dashboard, on the regional map, and on each station's detail page. Derived metrics like dew point, feels-like temperature, and VPD are calculated automatically when temperature and humidity are available.

No. FarmWeather is completely free. It's a community project — the more stations that join, the better the picture for everyone.

Your account and stations are set to Public by default when you register. This means your weather data is shared with the community straight away — and in return, you can see everyone else's public stations. You can change this anytime in your profile.

Public (default) — Your stations and readings are visible to other registered users who are also set to Public. Your data appears on the regional map and in community averages. In return, you can see everyone else's public stations. This is the recommended setting — the whole point is to share weather data across the community.
Private — Only you can see your own stations and data. You won't see other people's stations either. Useful if you're just testing or want to keep your readings to yourself.

Think of it as a fair exchange: if you share, you get to see what others share.

Without registering, you can see the home page with regional weather averages, the 7-day forecast, spray conditions, the planting calendar, and Farm Tools (GDD, ETo, fire danger, frost risk). The map shows all defined regions with regional summaries. The FAQ, planting calendar, and Farm Tools pages are also open to everyone.

Individual station markers, detailed station data, history charts, and alerts require a free account. Registration is quick — your account defaults to Public, so you'll immediately see every public station on the map with live data.

You have three options:

Ecowitt station (e.g. GW1100, GW2000, HP2551) — These are affordable, reliable, and send data directly to FarmWeather via Wi-Fi. Prices start around R1,500 for a basic model. This is the easiest setup.
Any WU-compatible station — Davis, Ambient Weather, Fine Offset, etc. If it can upload to Weather Underground, it can upload to FarmWeather using the same protocol.
Nothing at all — Set up a manual station and record readings by hand. Even a simple rain gauge and a thermometer from the co-op will do. Enter your readings on the website, by email, or via the Telegram bot.

Once registered and logged in, click Stations in the menu and then Add New Station. The setup wizard walks you through four steps:

Choose your station type (Ecowitt, WU, or Manual)
Give it a name and optional description
Set its location on the map (click or enter coordinates)
Review and save

After saving, you'll see your station's webhook URL and step-by-step instructions for configuring your hardware. For manual stations, you'll see how to submit readings by web form, email, or Telegram bot.

Manual stations support three ways to record data:

Web form: Open your station and click "+ Add Reading". Fill in rainfall and optionally temperature, humidity, wind, and pressure.

Email: Send an email to data@farmweather.co.za with your station name in the subject line. The body is parsed automatically — just type naturally.

Telegram bot: Link your account on your Profile page, then use /rain 15 to report 15mm rainfall or /hail to report hail. You can backdate up to 30 days — e.g. /rain 12 yesterday or /rain 8 03/03.

Accepted keywords:

Rain	rain, r
Temperature	temp, tmp, t
Humidity	hum, h
Wind	wind, wnd, w
Hail	hail
No rain	no rain, dry

Examples:

rain 14 tmp 22 hum 67 wind 13.5

r14 t22 h67 w13.5

12.5mm

no rain

If you just send a number (e.g. "15"), it's treated as rainfall in mm. Units and spaces between keywords and numbers are optional.

For automated stations (Ecowitt or WU), we recommend sending data every 5 minutes (300 seconds). You can configure this interval on your hardware. FarmWeather considers a station "online" if it has sent data within the last 15 minutes.

Manual stations update whenever you submit a reading. Even once a day (e.g. morning rain gauge reading) is valuable.

FarmWeather stores whatever your station sends. Common fields include:

Temperature (outdoor and indoor)
Humidity (outdoor and indoor)
Rainfall (daily total and rain rate)
Wind speed, gust, and direction
Barometric pressure
Solar radiation and UV index

Derived values like dew point, feels-like temperature, wet-bulb temperature, Delta-T, and Vapour Pressure Deficit (VPD) are calculated automatically when temperature and humidity data is available. VPD is particularly useful for crop management, while Delta-T is used for spray condition assessment.

The map shows weather stations in the Reitz area with colour-coded markers. You can switch between viewing temperature, rainfall, wind, or pressure using the dropdown. Click any marker to see that station's latest readings.

What you see depends on your account:

Not logged in: Regional averages only (no individual markers)
Logged in + Private: Only your own stations
Logged in + Public: Your stations plus all other public stations

The Spray Conditions card uses live weather data from stations in the area to work out whether it's a good time to spray — for both traditional (ground rig/boom) and drone (UAV) applications.

It checks wind speed, temperature, humidity, and a value called Delta-T (the difference between air temperature and wet-bulb temperature). Delta-T between 2 and 8 °C is ideal for traditional spraying; drones can tolerate up to 10 °C.

The card also warns about active rain and inversion conditions (calm winds after sunset with low Delta-T), which can cause spray to drift for kilometres.

These are guidelines based on SA agricultural best practice — always check the specific product label before spraying.

The planting calendar shows which vegetables and field crops to plant each month, tailored specifically to the Eastern Free State (Reitz area, ~1,600 m altitude, frost from late April to mid-September).

The "What to Plant" card on the home page gives you a quick summary for the current month. Click "Full calendar" to see all 12 months on a dedicated page.

On the full calendar page, you can click any vegetable to see detailed growing information — sun requirements, planting depth, spacing, days to harvest, watering needs, companion plants, and practical tips for our region.

The Farm Tools page brings together agricultural decision-support tools that are calculated from live weather data. You can access it from the main navigation bar or from the quick badges on the home page and station pages.

Growing Degree Days (GDD) tracks accumulated heat units from a planting date to estimate which growth stage your crop has reached. Select your crop type and planting date to see a progress bar with growth milestones.

Evapotranspiration (ETo) estimates daily water loss in mm/day, helping you decide when to irrigate. It also shows crop-specific water needs for maize, wheat, and pasture.

Fire Danger Index rates current veld fire risk from Low to Extreme based on temperature, humidity, wind, and grass dryness. Most useful during the dry season (May–October).

Frost Risk estimates tonight's frost probability during frost season (April–October), based on temperature, humidity, wind, and dew point. The assessment is most accurate from mid-afternoon onward.

Hay Curing Conditions evaluates whether the upcoming 2–3 day window is suitable for cutting and curing hay. It scores each day based on temperature, humidity, wind, rain, and sunshine, then gives an overall verdict from "Excellent" to "Don't cut". Choose between grass hay (2-day cure) and lucerne (3-day cure).

Livestock Conditions monitors cattle heat stress (THI), cold stress (wind chill with wet coat awareness), and daily water demand per head — helping livestock farmers plan shade, shelter, and water supply.

All Farm Tools indicators are calculated from live weather data using established agricultural and meteorological formulas. Here's what goes into each one:

Heat Stress — Temperature-Humidity Index (THI)

THI = (1.8 × T + 32) − (0.55 − 0.0055 × RH) × (1.8 × T − 26)

Where T = air temperature (°C) and RH = relative humidity (%).

Cattle thresholds: <68 Comfortable, 68–71 Mild, 72–79 Moderate, 80–89 Severe, ≥90 Emergency.

Sheep thresholds: <70 Comfortable, 70–75 Mild, 76–81 Moderate, 82–86 Severe, ≥87 Emergency. Sheep tolerate heat slightly better than cattle; wool breeds (Merino, Dohne Merino) are more affected than hair breeds (Dorper, Damara).

Cold Stress — Wind Chill

WC = 13.12 + 0.6215×T − 11.37×W^0.16 + 0.3965×T×W^0.16

Standard wind chill formula (for T ≤ 10°C and wind > 4.8 km/h). Wet cattle lose 2–3× more body heat. Freshly shorn sheep lose 3× body heat — the tool flags shearing season (Apr–May, Aug–Sep) and lambing season (Jul–Oct) automatically.

Fire Danger Index (FDI)

FDI = 2 × exp(−23.6 + 5.01×ln(C) + 0.0281×T − 0.226×√H + 0.633×√W)

McArthur Grassland Fire Danger Index (Mark 5), the standard used by SA fire services. C = grass curing % (estimated by season), T = temperature, H = humidity, W = wind speed.

Scale: 0–20 Low, 21–45 Moderate, 46–60 High, 61–75 Very High, 76+ Extreme.

Frost Risk

Score-based probability (0–100%) calculated from seven factors: current temperature (0–40 points), humidity level (±15), wind speed (±10), dew point (0–12), forecast minimum temperature (0–20), deep frost season bonus (+5 in Jun–Jul), and time-of-day adjustment. Designed for radiation frost — the most common type in the Eastern Free State.

Levels: <15% Low, 15–34% Moderate, 35–59% High, ≥60% Very High.

Evapotranspiration (ETo)

Estimated using the Hargreaves equation (when only temperature data is available) or the FAO-56 Penman-Monteith equation (when full weather data is available including solar radiation, wind, and humidity). Expressed in mm/day. Crop water needs are derived by multiplying ETo by a crop coefficient (Kc).

Growing Degree Days (GDD)

GDD = max(0, (T_max + T_min)/2 − T_base)

Accumulated daily from your planting date. Base temperatures differ by crop (e.g. maize 10°C, wheat 0°C). Growth stage milestones are based on typical GDD requirements for Eastern FS conditions.

Spray Conditions — Delta-T

ΔT = T_dry − T_wet

Wet-bulb temperature calculated using the Stull (2011) approximation. SA agricultural thresholds: traditional spraying needs wind 3–15 km/h, temp 10–28°C, humidity 40–90%, ΔT 2–8°C. Drones tolerate wider ranges (wind to 25, ΔT to 10). Inversion warnings trigger after sunset when wind < 5 km/h and ΔT < 2°C.

Hay Curing Conditions

Each day in the cure window is scored 0–100 from five components: temperature (20 pts, ideal 20–28°C), humidity (25 pts, ideal <55%), wind (25 pts, ideal 10–25 km/h), rain (25 pts, any precipitation = 0), and a solar radiation bonus (5 pts). Rain in the cure window is an automatic "Don't cut". Grass hay needs 2 dry days; lucerne needs 3. Recent rain (>10mm in 48h) also triggers a "Don't cut" verdict as fields are too wet to enter.

Verdicts: Excellent (avg ≥75, min ≥65), Good (avg ≥60, min ≥50), Risky (min <50 or avg <60), Don't cut (rain in window or avg <40).

Livestock Water Demand

Cattle: Base 22.5 L/day for a 450 kg animal at 15°C (5 L per 100 kg). Temperature multiplier scales from 1.0× at 15°C to 2.2× at 35°C. Lactating cows need 1.5× more.

Sheep: Base 5 L/day for a 60 kg ewe at 15°C. Scales to ~10 L/day at 35°C. Lactating ewes need 1.7× more.

Data accuracy depends on the station hardware, placement, and calibration. FarmWeather applies basic validation (e.g. rejecting temperatures outside -50 to 65°C or wind speeds above 300 km/h), but does not adjust or calibrate incoming data.

For best results, place your outdoor sensor in a well-ventilated spot, away from buildings and direct sunlight, and level your rain gauge so it isn't tilted.

FarmWeather is run by Neels from Reitz. If you have questions, need help setting up your station, or want to suggest improvements, send an email to info@farmweather.co.za.

Frequently Asked Questions