A moderate La Niña climate phase is expected through spring 2021. This indicates that slightly above average temperatures and slightly less rainfall than normal can be expected in California's avocado/lemon growing areas.
The fact that the winter weather pattern is expected to be warmer than usual doesn't rule out the possibility of a freeze. A freeze can occur any winter, regardless of the climate phase. And dry winters are often susceptible to sudden cold spells because of the lack of tempering effect of soil wet from winter rains
La Niña is one of three climate phases that are part of the El Niño Southern Oscillation (ENSO) climate pattern. Others are El Niño, during which colder and wetter conditions are expected in California, and neutral, when conditions are neither El Niño nor La Niña.
California's most severe freezes have occurred in weak La Niña, weak El Niño or neutral ENSO phases. Severe freezes in Decembers of 1990, 1998, 2001 and 2006 occurred after droughty years and years of low rainfall. In 2015, it snowed in Temecula and again in 2020 – in February!!! So cold weather is still waiting out there.
The most damaging freezes for avocado and citrus are advection and radiation freezes. In advection freezes, cold fronts move arctic air through the region. Radiation freezes feature overnight clear skies and light to no winds with periods of calm. Cold pockets and cold locations will have lower temperatures during radiation freezes. Break freezes and unsettled freezes are the other types of freezes.
During a radiation freeze, cold air drains down and pools in low areas. Know the cold pockets in your grove, and keep that air flowing with a wind machine, if possible.
Read the collected works on frost protection, frost damage and frost recovery here:
https://www.californiaavocadogrowers.com/growing/cultural-management-library/freeze-protection
It's also a good idea to be ready for fires in years of low/no rainfall.
The 2021 Weather Forecast from Fox Weather provided by CAC is below:
Image: Temecula snow on avocados in February
