I wish I could tell you a magic trick to make any rainy clouds disappear, but unfortunately, the only way I know to make them disappear is by closing my eyes and it doesn't help much. Here are a few ways to reduce the impact of the rain.
Weather forecasts, I know pretty obvious. This doesn't necessarily mean not to go out when it rains, but to plan accordingly.
Buy a good quality rain jacket, you will wonder why you paid so much for a jacket when it's sunny, but it will be worth every penny when the storm hits.
Have a fleece or wool mid-layer with you. I prefer a fleece since it dries much quicker than wool. Every rain jacket will let some water in at some point (if it rains long enough), so you will get wet no matter what. A fleece will make these wet inside-out days much more enjoyable since the material keeps some warmth and is relatively comfortable when wet.
Change your mindset that rain sucks! Think of it from a nature point of view, how it hydrates all the beautiful trees and flowers around you. You enjoy water when you're thirsty? Nature as well!
Being warm and wet is easy to tolerate but being cold and wet is miserable. Make sure you bring enough layer, stay active (in motion), drink enough, eat enough (lots of calories), and sleep well to stay warm in wet environments.
Watch for those creek crossings, they can flood greatly in periods of heavy rain.
Put your maps in a big Ziploc so you can look at them while they stay protected. Same goes if you navigate using your phone, a Ziploc bag will protect your phone from water and the best? The touchscreen works through the thin plastic.
Find shelter for your breaks if available (a big tree, a small cave, etc.)
For a baselayer choose polyester or wool. No cotton.
Pay more attention to your footing, wet rocks, roots, and leaves can be slippery.
Bring a separate set of sleeping clothes and socks (that you keep in the dry bag of your sleeping bag). Having dry clothes to change into at night (when you are soaked) will be worth every oz of its weight.
Line your backpack with a dry bag or a trash bag. Even the most watertight backpack with let some water in.
Keep the spirit high; sing, dance, visualize, talk, daydream, whatever works for you.
Carry extra food to have the option of a stay-in-camp day if the storm is too nasty.
Snow and rain are very similar, on cold days, I rather have snow than rain. You get wet at a slower pace and it is easier to deal with. In high altitude snow can linger in the spring and snow can fall even in the middle of the summer, if you are hiking in the summer, be prepared for some in higher elevation.
All the above tips about rain apply here.
The lowest the temperature goes, the more important it is to keep your layers dry.
Bring simple grocery bags, and wrap your feet (with socks) in it before putting your shoes. This will create a vapour barrier and trap your feet heat better. You will get wet from the inside but will work and keep you warm (same principle as neoprene).
The above tip works even in winter to prevent the isolation of your boot to get wet from sweat. Then you might want to have 2 socks, one inside the plastic bag one on top.
Same goes for your hands if you don't have proper layer gloves (plastic bags or large size hospital gloves does the trick)
If it's supposed to drop well below freezing at night, put some of the wet clothes in a grocery bag and keep it with you in your sleeping bag. This way you avoid putting on frozen socks in the morning (very unpleasant, to say the least!)
If a huge amount of snow is due overnight, wake up a few times during the night to make sure your shelter doesn't collapse because of cumulating snow.
Wind alone is rarely an enemy, except maybe on a narrow ridge with strong wind gusts. Yes, it is exhausting to fight against it, but its real threat is when it's paired with cold and wet weather. Then, you are dealing with an entirely different beast.
If nasty weather with wind is expected, make sure to bring a 4-sided shelter (especially in exposed places). A tarp will make you learn what stupid light is about.
Wear your rain jacket even if it doesn't rain, it is highly wind-resistant and will keep you warmer than a mid-layer.
On those narrow ridge, bring hiking poles and keep your steps small to stay balanced. If the wind is too strong, consider (if possible) to hike either on the left or the right side of the ridge using the ridge as a wind barrier.
Wind and rain can impact your night of sleep. That's why it is important to find a well-sheltered campsite even if the weather looks nice when you set camp.
Always look where the water would drain if it rains a lot. To be sure you are not camping in a dry (dry now, but not so dry later) creek.
I recommend if you haven't yet, to switch from a tent to a shelter (which is put up with your hiking poles). The first thing that will break under strong wind with a tent is the poles. Having your hiking poles as a support for your shelter over thin and light tent pole will make your shelter more storm proof.
Earplugs could save your night if it gets windy, the sound of wind gusts against your shelter might keep you up (if you are not the type that sleeps like a rock).
Using Y shaped tent stakes are much more solid and hold your shelter better than the V or I shaped one.
If the wind is so strong that you fear for your shelter. Put out your headlamp, pack up, and keep hiking until you find a better spot. Having your shelter collapsing on you (or even worse, breaking) won't change the fact that you will have to pack up and keep hiking, so better doing it on your own terms.
Avoid camping on hard ground. If it rains a lot, the hard ground doesn't absorb water well and will cumulate on top.
Avoid U-shaped campsites if you won't want to wake up floating around on a pool of water. If you have no choice, dig ways for the water to drain.