With petal fall well under way throughout the Valley, are you curious how the bees fared?

Warm temperatures and dry weather meant that 2020 turned out to be a good year for bees, paving the way for promising yield potential.


What is a bee hour?

Bee hours tells you how many hours have occurred which are favorable for bees to fly.

A bee hour is defined as one hour where:

  • There is no rain
  • The temperature is warmer than 55° F, and
  • Wind speeds are less than 15 mph
More bee activity means more opportunities for pollination, making bee hours a useful metric for getting a sense of how fruit or nut set, and ultimately yield, may compare between years.

In a study using data from Butte County, it was found that more bee hours led to a higher average yield. The relationship between bee hours and yield was small, yet notable , with only 17% of the variation in yield being explained by bee hours.

This is not surprising, as there are many other factors that can impact yield including frost, disease and post harvest water stress from the previous year. Furthermore, bee hours are only effective if they occur when bloom from cross-pollinating varieties are overlapping.

This is why it is crucial to count your bee hour accumulations from when bloom is first observed in your orchard.

2019 VS 2020 Season

In the following charts, we compare the daily bee hours and cumulative bee hours between the 2019 and 2020 season for Semios customers in different regions in California’s Central Valley.

The vertical bars represent daily bee hours, and the curved lines show cumulative bee hours.

Here’s what we saw:

Across the board, we observed consistent accumulations since the first week of February.

  • Total accumulations in February were 2 to 5 times more than last year.
  • On top of more accumulations, it is also more consistent compared to last year. Blooms are only likely to lead to nut set if pollinated within 3-4 days of blooming, therefore more consistent bee hours means that bloom that occurred at any time, will have a better chance of being pollinated.

The good weather persisted throughout bloom and is clearly seen by the significant increase in bee hours over 2019 numbers.

Although all that good weather meant an exceptionally dry winter, showers are expected in the coming days, which, hopefully, will be followed by more wet weather to make up for some of that rain deficit.

Daily Hours of Bee Activity in 2020 Compared to 2019 for a Colusa County Site


Daily Hours of Bee Activity in 2020 Compared to 2019 for a Madera County Site


Daily Hours of Bee Activity in 2020 Compared to 2019 for a Kern County Site


Want to know how your bee hours are compared to last year’s?  Contact your Account Manager to request a customized bee hour comparison report.


Griggs, W., & Iwakiri, B. (1964). Timing is critical for effective cross pollination of almond flowers. California Agriculture, 18(1), 6-7.



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