Walk into almost any taqueria and you can get agua de tamarindo, a refreshingly tangy Mexican drink made from tamarind fruit. But tamarind is not just Mexican, and tamarindo is not just a drink.

Up until last week, it hasn’t much looked like winter here in the Bay Area. Yet winter it is, and with it comes chillier weather, seasonal flus, and (we hope) days filled with rain. There’s little ...