Frosts after budbreak, 2007 to 2013

Here is a summary of 'frosts after budbreak' for the last 7 years here.

Budbreak is noted in yellow.  Frosts after budbreak are red. Frosts before budbread have low temps displayed, but the cells are not colored.

With the exception of 2012, there was a late frost every year.  2013 had the latest frost, May 4th.

The displayed temps were recorded at the WeatherUnderground site 'Possum Hollow'.  Possum Hollow is about 2 miles up river from us.  I've been spot checking its numbers with sensors in our vineyard, and the match is good. 

Since our interest here is 'frost' events, weather station records are not as useful as we would like.  The key temperature is surface temp, specifically leaf and bud temperature.  Weather station temps should be 'air temps', not surface temps.  Surfaces on frost nights are cooled significantly by the clear night sky.  Energy from the vines is simply radiated into outer space.

To get direct surface temps this year, we are looking at digital thermometers like this: Omega PT100 RTD Input thermometer.  These thermometers have traceable NIST certification.