A misconception about hiking in the outdoors is that you need to wear a lot of protective gear to fend off the elements. It is true that at times it will get cold and windy, or hot and sunny, but in reality the weather conditions shift erratically over different terrain and during different times in the day. Typically a hiker will get a good, early start to the day when the air is clear and crisp from the previous night. They hit the trail bundled up in gloves, a warm sweater and a sturdy jacket. Not long after setting out, as the hiker's pulse picks up from climbing uphill and the sun peeks out over the mountain top, she feels like it's getting too hot. If she's well-prepared she will be able to shed a couple of layers and move on, releasing a little heat but not getting a chill from the morning breeze. Later in the hike, as the clouds roll in through the valley, it starts to sprinkle a little and then becomes a torrent. Our hiker would soak if it wasn't for her weather-proofed Gore-Tex shell and backpack cover. The idea is to anticipate the conditions and be prepared to stop and adjust.
For each day of hiking you can plan out what you might need.
You would start with the basics of a couple of thin layers, then a warmer sweater,
and a shell. It's great if you have clothing that will also convert, such as
trekking pants that have a zipper at knee length to convert into shorts. Depending
on the climate and season you may need more layers, but that's up to you. Of
course you'll need some kind of shell that will serve as a windbreak, a rain
jacket, and something just to keep you warm and dry. Be sure to pack at least
one extra pair of socks and liners in case it get wet inside your boots. You
want to avoid the friction that builds up on your feet if there's too much
moisture. Once you've planned out your hiking day you need to pack all the
items in your backpack or day pack so that they are readily accessible. The
items you're less likely to need should go in first, to the bottom, then the
most immediate needs should go on the top or in an outside pocket that you
can reach in a flash. You'll find that you shift your layers a lot as conditions
change, but for every situation you'll be ready and very comfortable.