Damn, 1 minutes later and it's raining again.

Did get a quick try with One Shot AF, but didn't work. The lens didn't lock anything, even FTMing it back to focus it, the shutter wouldn't fire because the camera didn't think it was in focus.
And once on AI Focus, I kept pushing it back to in focus, but the camera just pushed the lens back to infinity-focus (OOF) and kept it there and wouldn't fire the shutter.

There's a custom-function to turn off focus-hunting, i'll try that next time it's dry outside. But for a 'real' answer on how well it works, it might take me a few weeks of practise...