At most Northern and Central California locations, accumulated fruit tree chilling from November 1st to February 10th was lower than a year ago in terms of chill hours (hours below 45°F). 33 of 37 selected locations had fewer than 80% of last year’s chill hours.*
In terms of chill portions as calculated using the more complex Dynamic Model,** however, only six of the 37 locations had chilling which was less than 80% of last year’s, all six being in coastal counties from Alameda to San Luis Obispo. In terms of chill portions, current season chilling to February 10th for Central Valley locations was generally similar to that of a year ago.
In Southern California as of February 10th, 14 of 26 locations had chill hours amounting to less than 80% vs. a year ago. There were also 14 locations (not the same 14) which had chilling portions of less than 80% of last year’s, including Chatsworth, Moreno Valley, San Diego and several locations in Santa Barbara and Ventura counties.
The data page, Chilling Hours & Portions: February 10, 2015, compares hours and portions for this year and last for 63 California locations. There is also a table comparing average fruit tree chilling of this year and last to the average of the previous four seasons for 12 northern and central California locations.
*Calculations based on data from the UC Davis Chill Calculator pages.
**The Dynamic Model for fruit tree chilling takes into account the varying effects of different temperatures including when they occur during the dormant period. The unit in this model is the chilling "portion".
photo: Mid-Pride peach February 13, 2015 at Hickman, CA