Until it has dried...
Tomorrow might not be a great day for using it - wet and windy...
Here are instructions from [broken link removed]
Where to use
Roundup kills most weeds around the garden on…
Gravel areas, paths, drives, patios, along fences and for edging lawns.
Can be used to clean up weedy ground before planting vegetables,
flowers, bushes and trees and to renovate overgrown areas.
BE CAREFULL, DO NOT USE ON LAWNS OR OTHER WANTED PLANTS,
unless you want to kill them.
Children and Pets should be excluded from the treated areas until dry.
How to Use
As good practice we always recommend that you where waterproof gloves and gardening footwear when using all garden chemicals. Roundup GC can be applied with either a garden sprayer or a watering can fitted with a fine rose or weed bar to lightly wet the leaves.
Do not apply through, store in, galvanised or unlined mild steel sprayers or watering cans.
Replanting and Sowing Light cover of annual weeds. Replanting or sowing can commence the day after treatment.
Dense cover including perennial weeds. Leave at least 7 days for the Roundup to move to the underground roots and shoots before digging or cultivating.
After application, rinse the sprayer or watering can three times and pour rinsing water over bare ground. When the bottle is empty, triple rinse and pour over waste ground.
When to Use
Roundup GC kills most weeds with a single application. Spray at anytime when the weeds are actively growing and have adequate leaf area to absorb the spray. You may have to retreat if it rains within 6 hours of treatment. Apply in calm dry conditions to avoid spray drifting onto wanted plants and lawns.