When to Water

Main page: Configuration
Previous: My Zones
Next: Schedules

The Setup → When to Water tab holds everything that controls when things happen: the automatic update and calculation times, the conditions that veto a run, how often watering is allowed, how multiple zones run, and the recurring schedules that actually trigger irrigation.

The order of a typical day:

1. Weather updates collect data throughout the day (see below).
2. The automatic calculation turns the collected data into a per-zone duration (default 23:00).
3. A recurring schedule (e.g. sunrise, finish before) waters the zones — unless a skip condition or the days-between limit vetoes it.

Automatic weather data update

If enabled, specify how often the weather-data update should happen (minutes, hours, days). You can also set an update delay to postpone the first update — useful in case your sensors do not provide a value immediately after Home Assistant starts.

As calculation needs weather data, make sure to update your weather data at least once before calculating.

Automatic duration calculation

If enabled, set the time of calculation (HH:MM). Calculation uses the weather data collected by updates to determine the irrigation duration. During calculation each zone consumes only the readings it needs (anchored to its own watermark) — the shared weather data is not wiped, so other zones keep their history.

Note: weather data is pruned automatically. Old readings are removed from the shared buffer once every zone that needs them has consumed them (with a hard cap of a few days). There is no "pruning time" to configure. You can still wipe everything manually via Setup → My Zones → Bulk Actions → Clear all weather data.

Skip Conditions

These settings let you automatically skip irrigation when conditions are unfavourable. All checks are independent — any one of them can veto an irrigation event. The dashboard's outlook banner shows you in advance whether the next run will likely be skipped, and why.

When rain is forecast

A single control decides how upcoming forecast rain affects watering. Requires a weather service to be configured.

• Ignore it — forecast rain is ignored; runs use the calculated duration.
• Water less — the upcoming forecast precipitation (summed over the look-ahead window) is subtracted from the deficit used to compute the duration, so the zone waters a little less. The bucket keeps the true deficit, so when the rain actually falls it tops the bucket up the rest of the way — the forecast rain is never double-counted once collected. If the rain misses, the next run makes up the difference.
• Skip watering — the run is skipped entirely when the total forecast precipitation across the look-ahead window exceeds the precipitation threshold (default 2 mm).

For Water less and Skip watering you also set the Forecast look-ahead (days) — how many upcoming forecast days are added together. The forecast starts at tomorrow (today is excluded), so 1 (the default) means just the next day, 2 the next two days, and so on.

Worked example (Water less). A zone has a 10 mm deficit and 4 mm of rain is forecast within the look-ahead window. The run delivers 6 mm and stops; the bucket is left 4 mm short, which the forecast rain is expected to fill. If the rain doesn't come, the deficit is still there and the next run waters it.

Upgrade notes. Before v2026.06.13 the look-ahead window was hard-wired to two days; the default is now 1 day (set it back to 2 for the old behaviour). The Water less option was previously a separate forecast-weighted durations toggle on the Experimental tab — it now lives here, backed by the same setting, so existing configurations are unchanged.

Skip on low temperature

If enabled, irrigation is skipped when the current temperature (from the weather service) is below the configured threshold (in °C). Useful for avoiding irrigation in near-freezing conditions.

• Default threshold: 5 °C
• Requires a weather service to be configured.

Skip on high wind speed

If enabled, irrigation is skipped when the current wind speed (from the weather service) is above the configured threshold (in m/s). Useful for avoiding evaporation or drift in windy conditions.

• Default threshold: 6.9 m/s (≈ 25 km/h)
• Requires a weather service to be configured.

Skip on frost

If enabled, irrigation is skipped when frost is expected, to protect pipes and plants from freezing. The guard compares two values and skips when the lower of them is below the configured threshold (default 1 °C):

• the current temperature from the weather service, and
• the forecast minimum for the coming night (the next forecast day).

This is distinct from Skip on low temperature: that guard looks only at the current reading, whereas the frost guard also looks ahead so a clear, sub-freezing night is caught even when it is still mild at run time. Requires a weather service to be configured. Default off.

Rain sensor

Optionally specify a binary_sensor entity. If that sensor is on when irrigation would normally fire, the event is skipped. No weather service is required for this check — it works with any binary sensor (e.g. a physical rain detector, a virtual sensor from a weather integration).

Leave this field empty to disable the rain sensor check.

Days between irrigation events

Configure the minimum number of days that must pass between irrigation events. This setting allows you to control how frequently irrigation can occur, which is useful for:

• Water conservation: Ensure adequate time between watering sessions
• Plant health: Allow soil to partially dry between irrigations
• Local restrictions: Comply with watering schedules or restrictions

How it works:

• Default value: 0 (no restriction - maintains current behavior)
• Range: 0-365 days
• When set to 0: Irrigation events can fire daily if conditions are met (default behavior)
• When set to a value > 0: Irrigation events will only fire if the specified number of days have passed since the last irrigation event

Example scenarios:

• Set to 1: Allow irrigation every other day maximum
• Set to 3: Allow irrigation only every 3 days minimum
• Set to 7: Weekly irrigation maximum

The system automatically tracks the number of days since the last irrigation event. If an irrigation trigger occurs but insufficient days have passed, the event is skipped and the days counter continues to increment. When enough days have passed, the next trigger will fire the irrigation event and reset the counter.

This feature works alongside the skip conditions above — if several restrictions apply, all must be satisfied for irrigation to occur.

Zone sequencing

When multiple zones have a linked entity configured and irrigation fires, this setting controls whether they run at the same time or one after another.

• Parallel (default): all linked entities open simultaneously. Each closes after its own calculated duration.
• Sequential: zones run one after another. The integration waits for each zone to finish before starting the next. Zones with 0 seconds calculated duration are skipped automatically.

Pump / master switch {#master-switch}

If a pump or main valve must be powered before any zone can water, configure an optional master switch here. The sub-settings only appear once a master entity is set.

• Master entity — a switch, valve or input_boolean the integration turns on before the first zone of a cycle. Leave empty to never touch a master (e.g. a pressure-controlled waterworks that starts on its own).
• Kicker (optional) — some pressure-controlled pumps don't restart promptly when merely powered; the kicker pulses the master off → pause → on to force a start. The pause is configurable.
• Settle delay — how long to wait after power-on before the first valve opens (pressure build-up), default 10 s.
• Turn off after irrigation (optional, default off) — off = the master stays powered (a self-monitoring pump); on = the integration turns it off after the last zone's planned end, and only once no run is still active.

The master applies to every path (scheduled, Irrigate now, and manual runs) and to both classic and self-closing zones.

Crash caveat: with Turn off after irrigation enabled, a Home Assistant outage after the master turns on but before the scheduled off leaves the master on — a non-self-protecting pump could dead-head or run dry. The integration can't prevent this alone; the master device must carry its own protection (dry-run cutoff, max-on timer). This is exactly why the option is off by default — a self-monitoring pump omits it and carries no crash exposure.

Recurring schedules

Below these settings, the same tab hosts the recurring schedules — the daily/weekly/monthly/interval/sun-based triggers that actually start irrigation. They are covered on their own page: Schedules.

Unit System Responsiveness

Smart Irrigation automatically detects and responds to changes in your Home Assistant unit system setting (metric/imperial). When you change the unit system in Home Assistant:

• All sensor entities immediately update to display values in the new units
• The web interface refreshes to show measurements in the correct units
• Stored configurations like precipitation thresholds maintain their values but display in appropriate units
• No restart or integration reload is required

This ensures seamless transitions between unit systems without losing your configuration data.

Main page: Configuration
Previous: My Zones
Next: Schedules