Well, think about it...it wasn't always grown indoors....so clearly mother earth can do a fine job with it. That being said, you are basically putting yourself at the mercy of nature when you put them outdoors. Yes, there is potential for massive downpours or a drought or something to kill your plants...but that's a risk you take growing outdoors. A drought you can fix by bringing them water...endless downpours may drown them, and there's nothing you can do. As for the clouds; is it pitch black whenever it gets cloudy? No, plenty of light still gets through, so that definitely won't kill your plants. Disease and pests (insects and/or larger animals) are your biggest potential problems though. Those are the things you should worry about.
Go for outside and do the best you can. If it doesn't work out so well, then go fully indoors for your next grow.
Oh and what size pots are they in? If you're just gonna keep them in their pots outside, then you want at least 3 gallons (and I'd recommend 5 gal for really nice plants).