Weed Killer Application: Why Evening Beats Morning in Hot Weather

The Temperature Warning

Labels prohibit application above 90°F because heat accelerates plant metabolism, making grass more susceptible to herbicide damage.

Morning vs. Evening

• Morning: Temperatures will rise soon—increases risk.
• Evening: Temperatures are falling—safer for the lawn.

Additional Factors

Drought-stressed or unhealthy grass is more easily damaged. Only spray when grass is actively growing and well-watered.

Best Practice

Apply herbicide in the early evening on a calm day when temperatures are below 85°F and no rain is forecast for 24 hours.