Update on weather conditions for thinning - June 3

Thursday, June 3, 2021

Last year's thinning conditions coincided with a heat wave. In many cases thinning programs worked well in the heat because it gave chemical thinners the necessary warmth for good activity. In a few cases, overthinning might have happened. Let's quickly compare the 2020 thinning weather with the weather forecast for the next week. 

Figure 1 is a screenshot from the weather forecast last year at thinning time where I have superimposed the actual observed weather conditions in red text. The average daytime temp across that week in 2020 was 27.9°C.

Figure 1: A screenshot of last year's weather forecast in 2020 at thinning time (7-12 mm king fruit diameter) with actual observed temperatures superimposed in red text.

The weather forecast for this year’s thinning period keeps getting warmer. Figure 2 is a screenshot of the forecast for this week in 2021. This year the daytime forecast is now averaging 26.9°C across the week. So it looks like daytime conditions are going to be fairly warm and similar to last year if the forecast is true. June 7th will be especially conducive to thinning if the nighttime temp is above 18C.

Figure 2: A screenshot of this year's weather forecast in 2021 at the start of the thinning period.


This post is not meant to cause concern and the information is being shared simply to compare our forecast conditions with those of last year. Knowing how the forecast compares to last year could be factored in to this year's thinning decisions. There is no need for concern about rates that worked for you in the warmth last year. If however, you thinned too aggressively last year in the heat, you might want to reduce rates in those situations where you got overthinning.

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