One of the things that can ruin a great day of riding is getting caught in an unexpected rainstorm or sudden drop in temperature.  And it's not just unpleasant - it can even be unsafe.  Hypothermia is something to take seriously if you spend time in the outdoors, whether riding or going for a day hike in the country. But what if you don't want to have to carry a big, bulky rain slicker, like the kind you wore to school as a kid?   Well, there are many good options.   One of the least expensive is to keep a disposable plastic rain poncho with you.   I recommend that you carry one of these in your basic toolkit at all times, for yourself, or maybe someone riding with you who isn't as prepared as you are! These are not bad to have as a backup, especially if you live in a predictable climate where you can be relatively sure whether or not you are going to get rained on (I'm looking at you, Southern Californians!)  But these are just that: disposable.   You'll get one use out of them, maybe two, and the one size fits all aspect means that they're never as comfortable as you might like.   Plus, they don't breathe, so you often get a clammy feeling wearing them.  Still, it's better than getting rained on or getting caught out after dark when the temperature drops, and having a miserable, cold, shivering ride home. Even more basic: a plastic trash bag - the big kind for outside barrels.   Make a hole in the bottom and poke your head through, slit halfway up each side so your arms can get out.  Again, better than nothing, but only barely! However, for the rest of us, there's a much better solution, and that's a lightweight rain jacket.   There's many of them available on the market and I've had a number of them over the years. My personal favorite is the Pearl Izumi Elite Barrier Jacket.   I've had my current one for a few years now, and it's almost always with me in my backpack, whether I'm riding or not.    It only weighs a few ounces and it folds up into one of its own pockets, the resulting package is about 5 inches square and 2 inches thick, but it compresses down so small that you can fit it in a jeans pocket, about the size of an apple, and half the weight! I find that they last about 5 years, if taken care of properly.  Don't wash them in the washing machine and certainly don't put it in the dryer.   There's no need to, anyway.  Cleaning one is a simple matter of just soaking them in some mild detergent in the sink for a bit and hanging to drip-dry.   Once in a while, a treatment with a rain repellent spray helps renew the water resisting properties.   Since it's a lightweight jacket, it's my favorite when it's raining, but 70+ degrees out and I'm exercising - I stay dry, but I don't get hot and sweaty.  In New England it's my summer rain jacket/windbreaker and it's good for keeping the mosquitoes off at night, too.  The rest of the year, it's there as backup.  You can choose a high-viz color like yellow if you like, for safety reasons.  Or if you don't particularly want to look like a school crossing guard, there's lots of other options available. Pearl Izumi has been around for over 50 years, and is known for making high quality gear at reasonable prices, widely available at cycling and sports stores, and online. My  personal shopping secret for bike clothing:  buy last year's model.   It's usually available for half-price or less.   As an item of clothing, it is subject to the laws of fashion that say that you're behind the times if you don't have this year's new version.    Silly as this sounds when considering an item of utilitarian clothing like a rain jacket, it still happens.  So save big! Here's two, one men's and one women's, currently at Amazon: http://www.amazon.com/gp/product/B00FZIPEC6 http://www.amazon.com/gp/product/B00CN2DQD6 You can also search the site by name and maybe even find a bigger bargain in an unusual color or size, if that works for you. Highly recommended!!