Interesting question - another aspect is what is the definition of a gust? When I looked this up a while ago in the UK it was a change in windspeed of 10 kts or more from the mean speed.
Crosswind components are not factored so the most pessimistic figures should be considered (ie max angle off runway and max gust etc) although that said wind checks on final approach tend to be instantaneous but there can be a big difference between tower reported wind and what its actually doing at touchdown or on the runway.
As far as performance is concerned remember that headwinds are factored 50% and tailwinds 150% but calm is not factored at all - important to remember if you have assumed calm for perf calcs and there is actually a light tailwind.
Hope this helps