How long after I apply my weed & feed liquid fertilizer, can the lawn be watered, or if it rains? I applied it 21 hrs. ago, and it's raining. Will this affect it?

Weed and Feed should be allowed to dry at least 1 day, then thoroughly watered into your lawn. Rain now is OK, However if the soil is too dry, hard and compacted, some of the fertilizer may get washed away.Liquid fertilizers are systemic meaning they feed through the roots of the plants, and through the foliage. Weed control enters through pores on the leaves of the weed and translocates through its system. The longer its allowed to dry, the better the results.During summer months granular slow release fertilizers are better to use. When applied properly, they will not burn the lawn since they are encapsulated in a polymer and begin feeding when watered into the soil. Granulars only feed the roots. Liquids may burn the foliage when its hot and dry, and should only be applied in spring and fall when the ground is moist and temps are between 50 and80 degrees. Using a spot sprayer for weeds is more sufficient during summer. If at any time it rains right after any application containing weed control it may be necessary to reapply product to the lawn, wait 1 week to see if the weeds are beginning to curl, if not then reapply.

I tend to agree with pdr but it really doesn't matter at this point. The application is done and its raining, if the chemical is going to fail to do its job there is not way to avoid it. If you do not see expected results in a week, read the label regarding reapplication. You should be OK with a slightly reduced concentration.