[API] Forecast Rain Amount

Please add a forecast rain amount to the daily forecasts in addition to the % chance of rain. It would be helpful for planning irrigation or just generally having an idea how planned activities could be impacted. This was a very useful feature in Dark Sky and I miss it in the Tempest App.


I think a forecast for the amount could not be possible very precise as rain often is a quite local event.
So ther might be only some rough ranges of ammount.

One step back… when rain is rain? O.K. Each falling water to the ground is a possible definition. But is a single drop a rain event ?

Nowadays there are plenty of forecasts available that do show the total amount of rain, so it should be possible.

I think a single drop could be enough for the unit to detect and report rain. That would count as a rain event… computer wise. Human wise I wouldn’t call that rain but how many drops do you want? That would get very subjective.


Does anyone knows a commmon metrological definition ?
I remember here had been some discussion on the rain probability percentage.
And here is the related question, at how much participation thoses probabilities are counted as 100% rain event.
As I understand the probability is to read as : In that percentage of similar weather situations there was rain. Hence the forecast suggests rain at these probability.

I’m a bit confused. In the forecast there could be two things with probabilities. One is the chance that during a certain period of time it will rain (the amount doesn’t matter) and the other is a prediction of the amount as rain (in ml or inch) that will fall during a period of time.
A rain event happening in my perspective is just the same as saying it rains. So the first of these two could have been defined as the chance that during a period of time a rain event will happen.

Yes, it’s the only reason why I still use another app for forecast. So I can see how much rain / snow is coming. Weather Underground has a nice way to display the precipitations quantity in it’s forecast for example.

I’m surprised this doesn’t have more votes. I am constantly annoyed that I have to go elsewhere to check the rain/snow forecast.
I am rather proud to have the only Tempest in my area, but when I send people a link to my Tempest page, I am actually a bit embarrassed that it doesn’t have the forecast. :pensive:

But I think when the AI feature gets working, this should be possible, but may need some more development work.

FYI, this data is available in the better_forecast RESTful API – the hourly forecast items include the expected accumulation (the “precip” field). Generally this data only seems to be provided when the hourly likelihood is high (>= 50%? I haven’t analyzed closely).

It would be very nice to provide this in the app, though!


  • I have seen accumulation specified in the better_forecast API for hours when the chance is as low as 35%
  • As an workaround (and potential help for neighbors), lately I’ve been working on an iCal calendar feed so that I can see accumulation at a glance in my phone calendar:

I’ve also worked on iCal feed for past observations:


I’d like to bump up the need for an estimated rain amount be included in the daily forecast. A forecast of x% of rain is meaningless without a quantifiable amount being given. Even for personal planning, there’s a huge difference between a 40% chance of light showers vs a monsoon.

I notice my RainMachine lawn sprinkler provides less accurate watering when my Tempest station is used alone as its weather source. Consequently, I’m forced to add the nearest NOAA weather station 10+ miles away

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I moved your post in here as it will also increase the vote count. Will have more effect than making another topic for the exact same request with 1 vote.

i would give it my vote, but they are all used up

I notice my RainMachine lawn sprinkler provides less accurate watering when my Tempest station is used alone as its weather source. Consequently, I’m forced to add the nearest NOAA weather station 10+ miles away

How does your RainMachine use the Tempest forecast, and why doesn’t it use the accumulation predictions that are available in the Tempest API?

I would hope this was voted higher. It is the only reason I also use weather underground so that I can get snowfall amount predictions. Very important for those of us in snow country.
Help beat the competition! Add predicted snowfall amount!


Same here, even the weather channel and my local radio stations have this. How can a forecast be “better” if I don’t know I’m going to get .1” rain vs 3”. I live off a road with several low water crossings and I can’t go to the closest major town if we get >=2”, I have to go the other direction. If the forecast is wrong I need to go 30 mins out of the way to get home. Lacking this is a major gap that most services attempt.


Its crazy that so dope system havnt such a sample info…99% app does it have…guys please add this asap becouse if not you force us to use anothers app​:pray:t2::pray:t2::pray:t2::pray:t2::pray:t2:

Very much agree. I link my Ag watering system to WU instead of Tempest even though my physical sensor is a tempest. Its job is to decide how much water to add through irrigation to bring me to optimal water. It cannot do that without predicted rain amount and it does not use the advanced API data (and I’m not going to write an API code set to allow that even though I do kind of have access to the system code base).

But even for just personal use, do I plan a cycling group ride for tomorrow? 100% chance of 0.01 inch will not stop anyone in my group from riding but 25% chance of 3.00 inches will.

This is counter intuitive.

You are better here with less localized data, or maybe less sensitive data.

For this irrigation solution the finite data set that a localized station provides is misleading, unless you apply some “english” to the data beyond what WF provides.
Please note the large fluctuations in % chance of rain throughout the day data provided by WF.

It’s like having a HAIR TRIGGER on a gun, it’s TOO sensitive.

BETTER example: that’s why quality analogue irrigation sensors use a leather sensor. It provides a more variable, non-digital, interpretation of precipitation and evaporation.

For this use-case I would recommend using a more generalized forecast like from an airport, zip-code or other “area-based forecast” and not what WF is providing.

This is a GREAT use-case, and I will be interested how you solve the issue!!

Agreed! I bought the station to get better forecasts, and I still can’t use the app because it doesn’t predict rain. I’m forced to use AccuWeather or Wunderground, which defeats the whole purpose of buying the station.

I’m happy to contribute data, but I need to know the rainfall prediction amounts, or this whole thing is kind of pointless. THANKS