High winds and rain... I've definitely seen these 'scorch' spots on outdoor tomatoes when they first get hit with inclement weather. I agree with the advice to just prune em off.
Even my leeks have gotten scorched from being put out this year into wind, frost, etc. Sometimes I've put tomatoes out and had them lose literally all of their foliage, which was soft and tender due to indoor and greenhouse conditions, unfit for the real world. The new foliage that grows back is entirely different, very tough and ready.
The plants do just fine afterwards.
BTW if you're concerned about the rate of leaf loss, there's nothing wrong with pinching part or half a leaf. Personally I think it's good for the plants, stimulating the natural response to herbivores (eg probably increase of solanine) and making the plant less palatable to the preds.