if its perfectly dry and no wind then even if its off slightly it should be ok. is channel 5 ok throughout the day (i see you posted at nearly 5pm) ive seen this loads of times as i specialise in problems that sky cant/wont sort out.
channels fine all day then around tea time they start playing up, sometimes theyll go off friday pm and theyre back monday morning, with channel 5showing it the worse.
if this is the case then someone local to you has a radar detector in their car that theyre leaving turned on when theyre home. have a look in the windscreens of cars around you to find it and ask the owner to turn it off.
youd be surprised how common this is, sky know about it but wont tell you, theyll charge a call out and send an engineer, but they havent told their engineers about this.
hope it helps
dd