Most storm damage tree removal calls come in during Gauteng's summer storm season, from about October to March. Five things cause most of them.
Short, violent storms. Highveld thunderstorms bring strong gusts, hail and heavy rain in a short burst, often in the late afternoon.
Waterlogged soil. After a few days of rain, roots lose their grip. A tree with a heavy crown can then pull its whole root plate out of the ground.
Gum trees. Gum trees grow tall and carry a lot of weight up high. Like several other large trees, they can drop a healthy-looking limb on a calm, hot afternoon, which arborists call summer branch drop.
Shot hole borer. The polyphagous shot hole borer was first identified in South Africa in 2017, and Gauteng is the centre of the outbreak. The beetle causes branch dieback and often kills the tree. A 2024 study found it in about 3 in 10 of the trees researchers checked in Houghton Estate, Johannesburg. Dead branches turn brittle and can drop without warning.
Lightning. Gauteng's summer storms bring frequent lightning. A strike can burn the wood or roots inside a tree without obvious damage on the outside, so have a struck tree checked even if it looks fine.