It's just after sunrise at the House Mountain Vineyard where we're harvesting the first pick of Petite Sirah.
Being in Arizona, monsoon activity is a factor every year in deciding when to harvest. (Monsoon is a term that is used locally to denote our intense summer storms.)
We may put out the call to harvest if we're expecting a big storm, or we might have to wait to harvest the grapes until after things dry out and the numbers (Brix and acids) fall in a favorable range again, since rain lowers Brix.
[The Vineyard Managers test the grapes for sugar in Brix using an instrument called a refractometer. They also test pH, and the cellar will often run tests for TA (titratable acids). When these numbers fall where the winemaker wants them, the grapes are ready for harvest.]