Leaf scorch develops when the plant uses water faster than it can absorb water from the soil. It's most likely to happen during drought, when high temperatures and hot, drying winds develop. Tender tissue along leaf margins is usually affected first, though any part of the leaf may turn brown if the unfavorable conditions continue. Maple (Acer), red oak (Quercus rubra), and flowering dogwood (Cornus florida) are most susceptible to leaf scorch. 

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Trees with limited root systems are especially susceptible to scorch. Recently transplanted trees that haven't had time to grow extensive root systems are obvious candidates. So are trees whose roots have been partially removed by digging near the tree or covered with a nonporous surface such as asphalt or concrete.