California water year

There has been an unusual weather pattern in California over the past few months, which could possibly have implications for the 2018 almond crop.

The Californian water year runs from October until September of the following year. In an average year, most of California's rainfall (over 80%) will fall in the first six months of the water year, from October until March.

The first three months of the current water year have proved to be unusually dry: Around Fresno, in the heart of California, there was only 12 mm of rainfall between October 1 and the end of December. Looking through the historical data, I could only find three other years in which Fresno experienced comparable low levels of precipitation in the first three months of the rain year: 1958, 1959 and 1999.

There was some rainfall earlier this month, but even so, from October 1 until the middle of January the total precipitation in Fresno only sits at around 31 mm. According to the historical average, in the first six months of the water year, over 200 mm of rain falls in the first half of the year. So if this Californian water year is going to end up in anyway comparable to the average year, an awful lot of rain has to fall over the next ten weeks or so to make up for the shortfall.

This could mean that there is  an increased risk that inclement weather might disrupt the almond bloom, which is only four weeks away. Indeed, if you look at those three other years which had a similarly dry start to the water year, in all cases the level of precipitation in the successive February was well above the historical average.

There have been some fears of a bee shortage in California this year, as may bees were killed in the Ventura County fires that raged at the end of last year. Thus, if the Californian almond growing regions are hit by inclement weather during the pollination, it could be particularly problematic given that there could be insufficient bee numbers this year.

Another possibility is that the dry weather over the past few months could signal a return to drought conditions in California. This would probably bode well for the 2018 almond crop, as a dry year following on from a wet year typically results in a solid almond crop. But of course, if the drought was to continue into 2019, things would start to become difficult for almond growers, particularly in the drier, southern parts of California.

So California could be headed into another drought, or we could see a disruptive deluge during the pollination next month, or perhaps something else altogether. Certainly, California looks like it is set for some more odd weather this year.