How long does weed killer need to be applied before rain? For best results, we recommend using Roundup® Weed & Grass Killer products on dry, warm, wind-free days. But if it's about to rain, fear not — all of our products should dry and become rainfast within 30 minutes to 3 hours — some even faster. The products below have a rainfast range of 10 minutes to 3 hours.
Can I use weed and feed in the winter?
Do Not Use It During Winter
Regardless of the type of weed or grass, applying weed and feed during the winter will have absolutely no effect on the appearance of your lawn in the following spring and summer. Hence, weed and feed is most effective when applied in the spring and fall.
Can I spray Roundup After rain?
Spraying After Rain
After it rains, wait until the leaves dry before spraying them with Roundup. This sometimes takes hours, especially in cooler weather or if there's high humidity, so try to plan your Roundup application when rain isn't expected.
When should I apply weed killer in spring?
The general rule is to apply your pre-emergent herbicide treatment after the ground has thawed from the winter but before the temperature of your soil reaches 55 degrees, as that is when crabgrass begins to germinate. Other weeds will germinate when the soil temperature is between 55 and 65 degrees.