Hi Badger,

Don't worry, it really is perfectly normal, especially in such an active
cat.  If he will let you (my cats always have), wet your hands under the
cold tap and stroke his fur to lightly coat it with water.  As this
evapourates, it has a cooling effect.  I had one cat who would always come
to me in hot weather and 'ask' for his 'wet wash', which is what I called
this activity.  He would come to me many times a day for this service .. he
loved it!

When you're not applying a 'wet wash', your cat will tend to lick its fur
more to create the same cooling effect.  He will also be shedding more fur
than usual in order to thin his coat.  Because of this, it is a good idea to
administer a hairball remedy so his gut doesn't become blocked with fur.
Make sure he can eat grass at will, as this is a cat's natural way of
dispelling a hairball.  If your cat attempts to vomit, but only produces
mucus and part-digested grass, this is a sign that he is having trouble
passing the hairball.   Even this is relatively normal, but don't let it go
on too long.  Insist your cat has hairball remedy, or ask your vet if there
is a pill you can give to ease the hairball's passage from your cat's gut.

N.B.  Hairball Remedy (Kittymalt in the UK) is a palatable malt-flavoured
paste.  Most cats will lick it from your finger, but you may need to be more
'persuasive'!

As well as the above, it is essential that your cat has plenty of fresh
water - indoors and out - as panting (or gaping, as it is sometimes called)
will quickly dehydrate your cat.

Hope this helps.
Spider

Yes, Badger, it is normal for cats to pant.  Just like dogs, it is their
way of sweating. Don't feel like an odd ball, my cat Parris does it too!