Perhaps we should also comment that the definition of a gust is 10 knots or more from the mean wind speed.
The wind passed by ATC should be the average over the previous 2 minutes. I say this with all respect but minor airfields are rarely equipped with an averaging device and/or a bespoke aviation anemometer which is suitably sited. This means that wind readouts at these airfields are no more than advisory and of course there can be a significant difference between the reported wind and actual wind at near the landing threshold.
To some extent the wind is always varying but in terms of aircraft control during take off and landing it's the degree of variability that matters.