At 09:30 (BST) on the 8th June, OWM was reporting 44mm/hour of rain (very heavy downpour) on both your main website and also via your current weather api. I have a screen snapshot of this but cannot see a way to post the image here. There has been a dry spell in Cupertino, US so this looks suspect.
At the same time, you were reporting Humidity of 35% which does not correlate with heavy rainfall. So this looks like an error in the model. I also note that OWM was reporting heavy rainfall at 05:00 (BST) on the 7th June and again at 06:00 (BST) on the 9th July. No other weather service was reporting rainfall.
The api call was: "http://api.openweathermap.org/data/2.5/weather?appid=<REDACT>&units=metric&lat=37.3230&lon=-122.0322"
Since, I am also logging your Forecast api for this location, I can confirm that NO rain was being forecast during that period from 7-9 June. So this looks like a disconnect between your current and forecast api.
I can provide data if you required. I submitted a ticket via the "Wrong Data" link on the web page showing the incorrect information.
Thank you for report.
Please share available data dumps using firstname.lastname@example.org