To start I am new to photography so someone more knowledgeable will probably drop by and give an answer better than mine, I had to laugh when I read your post though, reminded me of my own frustrations not too long ago!
...out of interest what lens is it? I'll take a stab at 18-50 kit? First off good luck to ya!!! LOL, I used to use a 18-50 with no manual focus ring, got so sick and tired of missing shots due to bad focus I almost threw the thing in the bin, in the end it's a good paperweight and I bought a Canon 17-85mm which has a manual focus ring... much better imho. I actually bought a Tamron 70-300mm(On special at Hervey's for $159) first and after finding how much easier life was with the manual focus ring bought the Canon.
Now there is a few ways, firstly you can try arriving during the day to where you will shoot storms and focus either manually or on auto at the furthest most visible thing, like a mountain ect. and then don't touch your setup again, I have heard of marking the spot on the focus ring and lens body, but in the end this method can be pretty dodgy, temp changes will affect the lens focus, so doing this possibly in blistering afternoon heat and then shooting at night... the temp change will cause the focus to change, IIRC!
Second method, which works ok but can be even more frustrating at times is using auto focus at night to focus on a distant light source, it does produce IMO better results than the first method but is dependent on having the distant light source which isn't always available so it becomes counterproductive at a certain point. There are different ways of doing this, you can just run test shots, ie. auto focus on the light source, once in focus flip the switch back to manual and take a test shot, if it's acceptable then you can move on or you can flip back to auto focus and have another go, another way is to enter live view shooting and “zoom in” (in the viewer-not on the lens) on the light source then focus on auto until the desired result is achieved and again flip back to manual focus and set the camera to your lightning shot settings. I still found this way frustrating not just because of always having to have a distant light source but also because I found changing focal length wrecks the process and you need to refocus... frustrating.
In the end it’s all about the fun of it…good luck!