Ok, don't panic. There's no reason why your Honda CBR250R should get destroyed by the raining season, as it has excellent build-quality. The most important things is regular washing – at least once a week, and at least twice a week when the roads are covered with water. This doesn't need to be a thorough scrub every time – just a good drenching to get rid of corrosive road scum. Avoid crashes by slowing down; and ditch your IRC tires for some with a higher road grip.
It's obviously also important to give your chain a regular clean and lubrication, at least weekly. Use a protective spray, on all exposed metal components, to minimize rust. It's more important to lubricate the cables through the raining season, too, so it's a good idea to give them a thorough service, including lubrication of the pistons, at least once, halfway though the raining season.
The toughest, most durable protection for paintwork is a protective plastic film, I saw some awesome stuff on my last visit to Sampeng market in Chinatown, Bangkok.
Yes, change the tyres, the stock IRC tyres are dangerous in the rain.
I'm going to have to run my new Honda CBR250R, nearly every day, right through the raining season. How can I keep it looking pristine?