What weather conditions make pruning risky?

Only prune fruit trees during acceptable weather. I once pruned in a drizzle (others also were pruning). A short while later, fire blight infected six apple trees, and more were damaged. Rain can spread bacteria through the fresh pruned cuts. Check the forecast multiple times during the week before your yearly pruning. Cancel your plans to prune if sustained wind exceeds 25 km/h (15 mph) or if the temperature falls below -5 °C (23 °F).

Become adjusted to regional extremes. My clients in Arizona will cut citrus trees at 5 Am as they are experiencing a heatwave. Growers in Minnesota will not cut an apple tree in January because the wood is frozen and it splinters very easily. Watch your soil temps; when the temps go below 4°C, (39°F) will delay healing. You can also use the NOAA 72-hour weather graphs to make reasonable estimates to figure out safe windows.

Recover from accidental weather damage from your shears by providing immediate care to the tissue exposed to the elements. After frost exposure, I sprayed some antitranspirant on all of the cuts to minimize moisture loss. For the branches torn off by the wind, cut them as clean as possible with sterilized spring-loaded spec scissors and varnish the wound with pruning sealant (only if you are in an oak wilt zone).

Read the full article: How to Prune Fruit Trees: A Step-by-Step Guide