Rain Accumulation Accuracy

The only substantial rainfall we’ve had since I installed my Tempest showed as 2.3" in my old plastic tube gauge and 1.59" on the Tempest. I imagine the tube is reasonably accurate as this is old technology. When I was looking into the Tempest, I got the impression that accuracy would be within 10% but I don’t remember where I read that.

Have users found their Tempests to be off by the same amount consistently or does it vary with intensity of the rain, wind, etc.?


Rain detection isn’t easy and in cases like you where rain is rare, the routines to learn have not much to crunch.

You can always help via a rain report, over time this will help your Tempest detect better and since you have the good old gauge … why not use it

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One of the main (many?) issues are light rain that are not detected and wind that causes false reading. Mix both wind and rain and you get pretty much unreliable values, far away from the 90% to 100% accuracy reported by Weatherflow (it’s mentioned on this page).

I’m pretty disappointed by the haptic rain sensor and if you browse the forum here, you will see that many people are.

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I live in Santa Cruz California where we just had our first significant rain of the season. My Tempest and all the others in the area seem to be under reporting the rain by about 90%. I have a “calibrated bucket” outside which got over 2" in the last 24 hours but my Tempest only shows 0.15". The nearby towns of Felton and Boulder Creek got over 2" according to the news reports but the Tempests in those areas are also showing in the 0.1" to 0.25" range. The error is WAY more than what Weatherflow says it should be. Thanks.

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@eric posted a response above which is a good response to your post, too. If you report the rain from your calibrated bucket then the calibration of your Tempest will be faster than if you just let the backend stuff try to calibrate it. In the meantime, you might want to enable RainCheck, if it isn’t already on.