My question is, “Why does everyday of the week show a 10% chance of rain”? It has rained 1 day in the last 90 days here in the Bay Area.

Where do you see this probability for rain in the Forecast Card or Forecast Page or somewhere else?

In case it isn’t being displayed on non-USA stations… [Screen Shot 2020-09-16 at 7.17.28 AM] [Screen Shot 2020-09-16 at 7.18.27 AM]

Oh I see. It is there as well in the rest of the World :wink: Thanks for that hint. @vreihen Do you remember (as I couldn’t find that quickly), I thought we had a topic or at least a discussion on that :thinking:

I think this was the post from David: [image] Rain percentage : hourly versus daily Tempest Owners There is some rounding going on, but @sunny is correct in general: The daily probability will almost always be higher than the hourly probability, but it is also not as simp…

You’re asking the person who doesn’t even remember what he ate for breakfast two hours ago??? :roll_eyes:

Exactly, Thanks @peter for helping my memory out :slightly_smiling_face:

A 10% round up is not acceptable in my opinion. I work for Oracle. If our software rounded up that much, we would be out of business. I think the calculations need to be adjusted. What brought this to my attention was that I gifted a Tempest unit to my father in law. He said, “It says there is …

As far as I can tell the probabilities in the forecast are rounded to the nearest 5% (0%, 5%, 10%, 15% and so on), so the maximum rounding is likely only 2.5% (i.e. up or down to the nearest 5%). The issue as David alluded to is that probabilities compound throughout the day. There is a higher chan…

It has rained 1 day in the SF Bay Area since June 1st. I think it is safe to throw up a 0% when the forecast is not calling for rain.

[image] peter: Again those very small chances compound throughout the day to give you the 10% you see. Actually there is more involved than just statistics or math to “compound” those values together. As dsj mentioned some of it is even secret sauce. But even mathematically it could be that …

Why does everyday of the week show a 10% chance of rain?

peter September 16, 2020, 11:34am 5

I think this was the post from David:

Topic		Replies	Views
Rain percentage : hourly versus daily Tempest Owners app , tempest	15	3208	October 28, 2022
Weather forecast for rain Tempest Owners tempest	10	141	February 5, 2026
Drop the 20% of rain tempest	7	1207	October 13, 2021
10 day forecast descriptions Tempest Owners	2	414	May 12, 2021
10 Day Forecast - % chance of rain	4	395	August 3, 2020

Why does everyday of the week show a 10% chance of rain?

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