Sounds like you have Pm, Or powdery mildew. Rain will likely lead to another format of mold, which is known as bud rot.
sounds like a bad infection of spider mitesI have got no mildewI was typing in quite of a panick so it was harder to undersrand, but when I look at some pictures of weed ready to be harvested, they look like they are covered with white web. Are my flowers supposed to be that developed for harvest ?
As posted, sounds like spider mites or PM. UNLESS, you mean "the pics you see of weed ready to be harvested", look like they have powdery white crystals (trichomes) all over them? If that's the case, then that's normal. White web, is not normal. But it looks like English may not be your native tongue. Best case, post some pics 
Photos speak all languages 
Great but is that first one ready to harvest ?
To know for sure get a 50x magnification glass!!
He's just trying to help, as we all are. You can tell when it's time to harvest by checking the trichomes I mentioned above. As Harris Hawk chimed in, you'll want to see cloudy trichomes with some, to 50% amber one before havesting. You can't see that without at least a 40X magnifier (microscope) : http://www.amazon.com/Carson-60X-100X-MicroMax-Microscope-MM-200/dp/B000P8AUMU/ They are cheap.
