As far as thunder storms goes, this is when a longer range open array radar really pays for itself, despite the opinion of some here that they are bought only because "they look cool". The internet/phone weather/radar tools are nice; I used to have a bunch of locations all up and down the east coast bookmarked in my Blackberry. But Freddy Furuno
gives a much better picture of how the weather relates to exactly where you are.
We are pleasure boaters, in that order. If it's going to be at all crappy out, we just as soon stay put another day, or two if necessary, and have done so many times. And not just for rough seas or high winds; if we have a beautiful area ahead we want to savor, then limited visibility due to rain or fog may keep us moored. On the other hand we've run the boat on instruments several times when it was foggy or heavy rain and the surroundings were not of particular interest.
As far as rough seas go, as discussed above, it depends. Of course it starts with the boat and it's capabilities, and the humans on board and their capabilities and tolerances. Have had some very pleasant cruising in long period 6 footers (on the beam, stabilized heavy boat), horrid cruising in steep, fast 2-3 footers with the wind roaring up or down the Pamlico, Chesapeake, Albemarle, even the LIS. Basically I don't like being out in much over 20 knot winds. Done it and more? Sure. Fun? Usually, no. We're in it for the fun.
In the protected canal and canal-like parts of the ICW, agree that weather is much less of an issue by far. But to the degree it may take the pleasure out of the trip due to poor visibility, why bother?