Absolutely. Applying pre-emergent too early in the spring means that you won’t have peak concentrations when springtime weeds start to germinate, making the pre-emergent useless. Similarly, applying it too early in the fall will cause similar problems since many weeds that grow in the fall don’t crop up until the weather gets cooler. In general, you need to wait until the soil temperature reaches 55°F before applying pre-emergent to get the best results.