oh no! I've just put the weed killer on and...

[cariboo]

...it's starting to rain! After weeks of dry weather. Rain was NOT forecast. Now, not half an hour after I've finished, thunder's rumbling, dark clouds gathering... what can I do? If anything? Do I have to re-do it when the rain stops or will I kill the entire garden?

Most weedkillers seem to need about 24 hours without rain (but if it doesn't rain after that, they should be watered)
There are products around though that claim only to need about an hour rain-free - what does yours say on the packet?

It doesn't say anything except not to use it on a windy day (duh!) nor if rain is forcast.