The absolute windiest time I've ever been out was last summer, I was going down a bank throwing a buzzbait when a wall of rain moved across the lakes at an amazing speed. It went from glass calm to hurricane force winds in a matter of seconds. Hit us hard, luckily we were nearby an empty boathouse that doesn't have a lift inside it, so we were able to take shelter in it. Barely got there though, our little 15 horse motor could hardly make headway into the wind. We later found out that a hurricane had actually touched down about half a mile from where we were, and winds were reported up to 75 miles an hour. This was on a small (360 acre) lake, so the waves didn't have as much distance to build as they do on larger lakes.
The time that I was closest to sinking the boat and the largest waves I have ever been out on occurred on a lake called Monroe (largest lake in Indiana, and of coarse we were fishing at the far side of the lake from the ramp). I was prefishing for a tournament there in early July and had been having a terrible day. We had fished from 6 am from 7:30 pm and only had one keeper, and we hadn't even been shaking fish off. Started seeing a storm build along side of the lake around 5:30, but for the next two hours it just seemed to run parallel to us. Since we had absolutely zero patterns going for the tournament, we kept on fishing. Then around 7:30 we got a call from someone who basically told us to get the heck off of the lake right now, the storm had just knocked out power to a huge part or the surrounding area with reported wind speeds of 40 mile an hour sustained with gusts up to 70. And it was looking like it was going to stop running parallel to us, and instead go right into us.
So we fired up the motor and got out of the cove we were fishing, and in literally 5 minutes the lake had gone from ~10 mile an hour winds to 40-70. Our 21' fish and ski (it has a way deeper v and handles waves much larger than a bass boat would, luckily) was getting waves swamped over the bow all the way to the wind sheild on almost every wave, filling the boat with water. By this point the rain was coming down so hard that we lost track of the shoreline, and the wave action was so jolting and the waves that we couldn't figure out were were on the small GPS screen we have mounted on the dashboard. We were driving essentially blindly, on an unfamiliar lake, with no view of the shoreline, and we couldn't even read our GPS.
We ultimately ended up finding our way into a protected cove where we hid from the wind for about 20 minutes, but the rain was still pouring down and the boat was filled with so much water that it was sitting dangerously low, even though the bilge pump was on. After that we decided to try and get back to the ramp again, this time by hugging the shoreline as lone as possible. By the time we got back to the main lake, the storm had calmed down and virtually disappeared, the rain had lessened and the wind down to a breeze.
The whole way back to the ramp we saw boats ran up on shorelines, bassboats and pontoons alike. Several had obviously ruined the hulls by choosing to run up the shorelines, apparently the owners thought that they had to do that to keep from sinking the boat with them in it. One especially nice Ranger bassboat with twin power poles had run up on the riprap shoreline, ruined its hull, and the back end was under water.
Never before had I actually felt like we were more likely to sink or flip the boat than not, the experience has definitely gave me a new appreciation to the power and danger of wind, especially on big lakes.
Coldest ever was a day with a high of 28 and a low in the single digits, with freezing rain that would freeze on your jacket, in addition to 10-20 mile an hour winds. No rain gear can keep you dry in that. By far the coldest I've ever been, but we caught a boat load of fish vertically jigging blade baits.