Weather update brought to you by Erika DeBrouwer, Tree Fruit Specialist
Weather continues to be reasonably warm during the day, further advancing apples but temperatures are dropping at night. Come Wednesday night (May 17) the risk of frost is high, although is not necessarily represented in forecasting data.
Sean Westerveld, OMAFRA Ginseng & Herb Specialist, stated in his recent blog post that the following factors could be cause for concern regarding a frost event:
- Low humidity and no recent rain: air cools more quickly
- Clear skies: further cooling air temperatures
- Negative dewpoint: dew/frost would not form until that temperature is reached and is a good indication of how cold it could get (refer to Table 1)
- Minimal wind, reducing frost or freeze prevention
Location | Lowest Dewpoint (°C) |
Collingwood | -5.0 |
Goderich | -3.9 |
Guelph | -7.8 |
Harrow | -2.8 |
Kingston | -2.8 |
London | -7.2 |
Oshawa | -7.8 |
Simcoe | -6.1 |
Trenton | -8.3 |
Vineland | -5.0 |
If the trees are stressed, which happens in the events such as frost, the impact that chemical thinners have may increase. Therefore it is important to be cautious when applying these products during the current weather conditions.
As a gentle reminder, here are the critical temperatures based on growth stage for apples: https://onfruit.ca/2023/04/17/the-horrid-f-word-frost-2/
During this critical time please prepare as best you can and think critically about any chemical applications.