Dew point is another way of saying the air is very dry. Frost is the result of radiative cooling, and the biggest things to worry about are: a very clear sky and no air movement. So low humidity will definitely contribute to a clear sky. Air movement can depend on local geography. If you're in a protected valley or dip, you are in more danger than if you are on top of a ridge, ceteris paribus. I'm at the top of a ridge and my first frost in fall is two weeks later than down at the bottom of the hill 1/2 mile away. And my last frost in spring is correspondingly earlier. So an extra month of growing season overall. So you can see why orange groves often fight frosting conditions just with big fans, then maybe some smoke, and when the air finally approaches freezing, then the sprinklers come on. My advice is to pay attention to the rhythms of nature as they play out in your garden, because that's the only thing that matters to you, and it can be surprisingly different from even a nearby area. If you want to get a dramatic feel for microclimates, just ride a motorcycle for a while! Bob E Tenn and a gloomy 41 degrees _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/… Unsubscribe: <mailto:pbs-unsubscribe@lists.pacificbulbsociety.net>