Always practice the proper pruning techniques. Lion-tailing or topping your trees makes them more vulnerable to disease, and sun and wind damage, no matter what time of year you trim them.
Topping the tree’s main branches to stubs will cause fast-growing sprouts to grow where the cut was made. This sounds great, but these sprouts are weak, and bushy. The new growth makes the tree uneven, and heavy. Extra maintenance pruning will be required to keep up with the additional, unbalanced weight.
If a tree is damaged or encroaching on signage or buildings, it can seem like a simple solution to only cut or “top” the portion of the tree that is a problem. However, topping trees has several negative effects on what is left of the tree. In addition to looking... weird... improperly pruning a tree in this way may leave the tree structurally unsound, and more prone to breaking.