Update on Heat Units and Precipitation

2021 Degree Day Accumulations

Jeff Franklin has shared an update on degree day accumulations, noting that our sizeable lead in heat units this year has retreated. He explained that in July, the mean temperature was 1.4 °C lower than the 10-year average (19.1 °C compared to 20.5 °C). Please note that degree days may not directly translate to a change in harvest dates but monitor blocks at least slightly earlier than usual to catch any signs of advanced maturity to be off to a good start.

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1st to August 11th for the past 17 seasons. Provided by Jeff Franklin (AAFC).

• Approximately 5% more plant development heat units compared to the 5-year average, and 5% more compared to the 10-year average.
• Approximately 3% more plant development heat units compared to 2020, and 13% more compared with 2019.
• Approximately 4% more insect development heat units compared to the 5-year average, and 4% more compared to the 10-year average.

Seasonal Precipitation

Jeff Franklin also shared the precipitation totals from Kentville, observing that, "Precipitation totals in July were approximately twice the 10-year average and already in August, we have received half of the expected precipitation for this month. Keep in mind, 50 mm of precipitation in July were received in a 45-minute period on the 21st from thunderstorms. This was a localized event and did not impact the entire Annapolis Valley."

Those people who are monitoring the NSFGA network of weather stations in ten different locations throughout the Valley will have the numbers to show how much precipitation has varied.

Table 1: Monthly precipitation totals in 2021 compared with the 10-year average. Provided by Jeff Franklin (AAFC).

	2021   Precipitation (mm)	10 Year Average 2011 to 2020 Precipitation (mm)
June	35.9	104.3
July	164.4	84.7
August	48.3***	90.2

                                          ***data for the first 11 days of August