Focus image during the night?

I have a Nikon D3100 and live in a part of Switzerland known for thunderstorms. I love to take pictures of them. The only problem I have is: I don't always get a sharp image since it's dark and can't focus manually. How would you do?

Look at your lens. There's a distance meter near the focusing ring. Chances are you are going to be shooting well beyond that range.so…
set the focus to manual
manually adjust the lens to the infinte marker
use a wide aperture (lowest aperture number your lens will go)
Make sure you hav ethe camera on a tripod ad use mirror lock up.
use 30 second shutter speeds with a remote. Just keep shooting since lightning is unpredictable you will end up with alot of images of nothing but with luck you'll get something eventually

You need to know where the infinity distance setting is on your lens.

Manually set it there and while using your camera on a tripod and in the bulb shutter setting, open the shutter for a few lighting strikes. You will have to adjust the aperture of the lens to assure proper exposure

Without knowing what lens you are using, I can't be precise, but since most "new" lenses don't have a mechanical infinity stop, it's hard to set focus to infinity precisely even if the lens has a scale. The best advice I can give you is preset your focus in the light of day, while in AF mode with the aperture setting you want, which should be either f/11 or 22 so that you have the most depth of field the lens can provide- focus lock on something far away, then flip your AF switch (on the camera or lens) to MF and tape the ring with electrical tape so it won't move. That's what I'd do.

Use manual focus.use the viewfinder to focus on relatively distant but brightly lit objects like houses or bill boards etc. And since you mentioned thunderstorms, i'm guessing your main target is lighting? In that you unless you have a lightning trigger, you have to use long exposure shots. Then you should use smaller apertures like f/11-20. This will ensure a wide enough depth of field to make sure everything is in focus in your image.best of luck.

Without knowing what lens you are using, I can't be precise, but since most "new" lenses don't have a mechanical infinity stop, it's hard to set focus to infinity precisely even if the lens has a scale. The best advice I can give you is preset your focus in the light of day, while in AF mode with the aperture setting you want, which should be either f/11 or 22 so that you have the most depth of field the lens can provide- focus lock on something far away, then flip your AF switch (on the camera or lens) to MF and tape the ring with electrical tape so it won't move. That's what I'd do.