Hi Vijaysahay, I can understand your feeling. I used to be the same when I got my bike. But realized it was getting insanity and possessive about the bike. About the maintenance of the bike. Water from above is pretty clean and harmless. It’s the oil/grit/rubber emulsion from the road that gums up your bike. Fenders will protect you and the bike from this muck, and avoid that charming brown stripe on your lower back. A helmet peak will keep rain of your glasses. In warm rain, its best to get wet.
In cool rain, wear a waterproof, but you have to modulate your work-rate so as not to sweat. In cold rain add rain pants, you need to pay special attention to your feet, either neoprene over boots, gortex under-socks, or more sensible, keep the darned water out in the first place with waterproof boots.
Wear bright colors, lights if necessary, keep your rims dry with braking, and maintain extra stopping distance