You'll be fine. My Gixxer has a lot more power than my STR but on the track its no problem. Oultons a great track but very nadgery, there's no time to rest and the bike never seems to be upright. I always come home knackered, partly because of the circuit and partly because the Gixxer needs to man-handled to get round the corners!
As for the day; It was a bit chilly to start of with and hail stoned once but it soon cleared up. All but two sessions were dry.
Book it, you'll enjoy yourself