California citrus growers got somewhat of a reprieve from extremely low temperatures the first part of the weekend, but mandarin and navel crops were likely damaged the night of Dec. 8-9, the sixth night in a row growers battled freezing conditions.

“Cold daytime temperatures on Sunday set the stage for a rough night, with wind machines starting as early as 8 p.m.,” according to a Dec. 9 statement from Exeter-based California Citrus Mutual. “Unlike previous nights, an inversion layer failed to materialize, leaving wind protection unsuccessful at keeping temperatures above critical levels. Coupled with longer duration at low temperatures, damage is anticipated for the already weakened fruit.”

Both navels and mandarins were likely hurt by the Dec. 8-9 freeze, according to Citrus Mutual. The first five nights of the freezing temperatures were not thought to have affected navels, according to the association.

The first two nights of cold weather were thought to have damaged mandarins, though one grower, Los Angeles-based Paramount Citrus, which markets mandarins under the Wonderful Halos label, did not expect significant losses as of Dec. 6.

Slightly higher temperatures the nights of Dec. 6-7 and Dec. 7-8, in addition to rain, which helped protect crops, provided relief for growers on those nights.

As of Dec. 9, California Citrus Mutual estimated the frost protection costs to the industry at $23 million.

Some growers are concerned that heavily-used wind machines could fail to work if the cold persists, or that not enough fuel could be found for them. After six nights, machines had run for an average of 56 hours each, according to Citrus Mutual.