Hot temperatures, growing degree days and wildfires

In July, California on average saw consistently days near, at or over 100 degrees Fahrenheit for max temperature. That heat has continued into August.

Vinsight weather app max/min temperatures

Comparing 2018 July with 2017 and 2016, average temperatures are also higher by a few degrees for most of the month.

Last half of July temperature comparison

Looking at growing degree days, 2018 started off the year pretty low but is now catching up with the warm spell in July/August. We have not seen this many degree days in July since 2006.

California Growing Degree Days by month

Now what does this mean for agriculture? It definitely shows consistently hotter temperatures during the months leading up to harvest compared to recent years. But because of the cooler weather we saw earlier this year, the warm temperatures are a nice balance as long as things normalize and start to cool down. The hot weather helped kick almonds back on track to be a record crop. And we see about an average year for wine grapes. Harvest has already started for both in the central valley.

Unfortunately, the warm temperatures aren’t helping the already dry conditions for fires. We have now seen the largest fire in California history with the Mendocino Complex at over 344,000 burned acres. The Mendocino Complex (The Ranch and River Fires) and the Carr Fire total over 547,000 burned acres.

Mendocino Complex fire — Sentinel 2 imagery
Carr Fire — Sentinel 2 imagery

Direct damage to agriculture has been limited. At this time, based on our analysis, only 11 acres of grapes have been consumed by the Ranch and River fires. There are still many vineyards just outside the fire zones that will have suffered from smoke taint from proximity.

Burned vineyards in black — Sentinel 2 imagery

There are currently 15 active fire incidents in California. Hopefully the weather will cool off soon and conditions will improve.


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