ZoneFlow

Rain without a gauge

Rain is the biggest thing ZoneFlow takes into account, and a rain gauge is the best way to tell it how much fell. If you have one, you don't need anything on this page. See A cheap DIY rain gauge if you want to build one.

If you have no gauge and don't want one, ZoneFlow 1.6.1 has two lighter options for outdoor zones. Greenhouse and indoor zones have a roof and don't use rain at all.

Option 1: type the rain in yourself

If you read a simple gauge by hand, a jar or a plastic rain gauge on a post, you can tell ZoneFlow what you read. Each outdoor zone without a gauge gets a Manual Rain number and an Add Manual Rain button. Set the number, press the button, and that rain counts against watering like any other. You can also do it from an automation with the zoneflow.add_rain service. It takes an amount and, if you want, the time the rain fell, up to 14 days back.

Option 2: borrow rain from nearby weather stations (experimental)

Forecast services often get their numbers from a station 20 km or more away. A private weather station a kilometre or two from your garden is usually much closer to what really fell on it. ZoneFlow can read up to three of these from Weather Underground and use them for the rain it credits against watering.

It is marked experimental for a reason. It is not 100 % reliable, and less so the further away the stations are. It only affects how much rain is credited. It does not forecast, and it doesn't replace the weather service that holds off a watering before rain. How useful it is depends on where you live: the USA and parts of Europe have many private stations, while in many other countries they are few and far apart.

Two checks before you start, in this order

  1. Look at the map first. Open the Weather Underground map and look for stations near your garden that report rain. Nearer is better: aim for within 1 km, and 2 km at the most. If there are none, stop here. This option won't help you.
  2. You need your own station to get the free API key. Weather Underground only gives keys to people who upload data. Register a station there and upload at least outdoor temperature and humidity. A rain gauge or a full weather station is not needed. The easy way is the ha-weather-uploader HACS integration, which sends your Home Assistant sensors every few minutes. Once your station is uploading, the API key is in your Weather Underground account under API Keys.

ZoneFlow only needs the API key. It keeps it in its own settings and never in the log, and it is removed from diagnostics downloads.

Setting it up

  1. Settings, Devices and services, Add integration, ZoneFlow, then Set up Weather Underground rain. It is offered once you have at least one zone, and you set it up once for the whole Home Assistant.
  2. Paste the API key and choose how far to search, from 0.5 to 2 km. ZoneFlow measures the distance from your Home Assistant home location.
  3. Pick one, two or three stations. Each shows its distance and today's rain so you can see if the numbers look sensible. Stations over 1 km away are marked: watch how their readings compare with the rain at your place for a while before you trust them.
  4. For each outdoor zone without a gauge, open Configure, then Weather Underground rain, and switch it on.

A zone with a rain gauge never uses Weather Underground.

How the rain figure is made

  • Three stations: the middle reading, so one broken gauge can't fool it.
  • Two stations: the lower reading. Too much rain makes ZoneFlow water too little, which hurts plants. Too little only waters a bit more.
  • One station: used as it is, and shown as lower confidence.
  • No usable station: nothing is added and the zone acts as if it had no gauge. After 6 hours without data a Repairs message appears and clears itself when data returns.

A station is left out when it hasn't reported for 2 hours, reports an impossible jump, or has shown no rain for 24 hours while the others did, which looks like a stuck gauge.

How often it checks

Every 2 hours normally, and every 10 minutes from an hour before a watering until it finishes, so the "is it raining now" check sees recent rain. It also checks once at 23:55 to catch the last rain of the day. That is far below the limit of a free key. Stations upload every few minutes, so "raining now" can lag real rain by up to about 15 minutes.

Is it good enough for your garden?

Compare the Rain today sensor with what you see outside. Also look at the new Forecast Skip Hit Rate sensor on a zone with a weather service. Each time ZoneFlow skipped a watering because rain was forecast, it looks 48 hours later at the rain that really fell and counts whether the skip was right. It shows how often the forecast was right for your garden, and it is a good number to watch whichever rain source you use.