Which Socks?

Wool.
Does all you asked about.

Fine wool (not the bulky scratchy kind), silk, or blends of the two work best for all the conditions you mentioned. Smartwool brand socks are mentioned a lot on this forum. All cotton are probably the least desirable, especially for fast drying and wicking moisture from your feet.

Wear the same socks you wear when you walk around all day at home.

Merino wool -- always.

I got some toe blisters a couple of years ago from the Smartwool Merino wool socks. It WAS during a heatwave in Paris and Germany. The next year I switched to Injinji toe socks which keeps each little piggy separated and I’ve been well pleased. They are wick away athletic socks and do keep my feet dry.

It depends upon the time of year and where in Europe. I agree with wool for shoulder season in cooler climates. My wife and I were in Poland and NE Germany the first half of this past May. Though it was warmer than we expected, I wore wool socks successfully. I like my Keens but you can also get good wool socks at Costco. For cotton socks Nike Dri-Fit are great. As with wool socks, you can wear these at least a couple of day without them feeling too grungy. For me that's a big deal because it saves me space when packing.

Darn Tough Socks are the best. Made in Vermont. They wear better than Smartwool and actually have a guarantee if you ever put a hole in them they will send you a replacement. They have all different weights, styles to fit any activity. I wear their thinner merino wool no show sox in my golf shoes and running/walking shoes.
This fall wore a thicker Darn Tough sock for a cold and wet golf tournament. Even though my socks were wet mt feet didn't get cold. It was 40 degrees.

Another Darn Tough fan here. Great when walking the Camino for miles and miles each day. Guaranteed for life.

I would not wear wool socks in the summer.

Here's one opinion: The Best Hiking Socks. FWIW, for me, a less demanding user, Costco's work fine.

Any seasoned hiker will tell you that a good pair of hiking socks is a must-have on the trail. But despite their simple appearance, hiking socks can be a complicated purchase. That’s why we spent 25 hours researching 65 sock options. Then we took to the trails of Vancouver, British Columbia, hiking for more than 75 hours, 160 miles, and 350,000 steps in 18 pairs of socks. Eventually we determined that the women’s and men’s Darn Tough Light Hiker Micro Crew Light Cushion socks are the best hiking socks for most people. Backed by a lifetime guarantee, these wool socks offer the ideal mix of comfort, durability, and cushioning.

Quality merino wool socks happily utilized winter, summer, fall and spring.

I wear high quality merino wool socks, thicker in winter and whisper thin in summer. I never get blisters.

Runners know that merino wool sox, like the Smartwool PhD line ( thin, smooth finish) are best for busy feet, in summer or winter.

Thanks for all the replies. You would think in my 55 years I would have some experience with wool socks, but can't recall EVER wearing them (unless those itchy ones from my grandmother . . . )

I buy only non-cotton socks. I literally look at materials and buy something that has no cotton in it. I have socks made by Underarmour, Calvin Klein, Adidas, etc. - all non cotton.

Cotton loses both it's cushion and insulation when it gets wet - whether from rain or sweat. Losing it's cushion makes you susceptible to blisters, which will affect your ability to keep walking. Losing insulation value can be a serious issue in bad weather.

When I camped in the Sierras as a teen, the mantra was "cotton kills" (not just socks but pants, shirts, sweaters). If you get wet, from a sudden rain or slipping into a stream, you have an immediate exposure risk. Cotton is slow drying and has nearly zero insulation when wet.

For most trips, I take crew socks, normally black, and I pack three or four pairs of identical socks. Last trip I packed short ankle/no-show socks because it was summer and that's what people are wearing. Every sock in my sock drawer was purchased with an eye toward traveling. I like to be able to throw things in my bag and go.

If weather is a factor, I'll pack something with wool content (and no cotton). The pack list for my next trip to Ireland in May will include either wool blend hiking socks or similar.

It's not just socks, I normally pack all non-cotton. I have been taking one pair of lighter weight slim-fit jeans lately.

Merino Wool ; regardless of weather.
They have super thin Merino Wool ones for the summer, normal ones for shoulder seasons and thick ones for winter.
A couple of good companies already mentioned above: Smart Wool and Darn Tough

If not comfortable ordering online, head over to REI, EMS or similar type outdoors store and you will notice all they sell are high end Merino Wool in the sock sections.

If you really want to treat yourself pickup a Merino Wool tee shirt as well and use that as a base layer in any weather.

Smartwool is my go-to brand at home and for travel, they have various thicknesses and styles that should suit pretty much any need, for men and women. I wear the short or no-show ones with my sneakers in summer and my feet do not get hot at all. Another brand that's great for blister prevention is Wrightsocks, the dual layers really do work.

Warren, I was in exactly your boat when I contemplated wool socks after reading about them on this forum. My memories were older than yours and still vivid. I am now a believer. Best for me is how much drier they keep my feet. I travel with them in warm or cold weather and they’re perfect for me. They were expensive but worth it. At home I get by with my cotton crews, but at home I don’t walk miles everyday. If the book is good, some days I don’t walk farther than the coffee pot.

I was sceptical about wool socks, too. I can't wear wool scarves, hats, or sweaters and suspected I would find socks itchy, too. It only took one pair to convince me, and now nearly all my socks are wool, including very lightweight ones that work on all but the hottest summer days.

Merino wool. Even for summer. I live in hot, humid Houston, TX, and even in summer I wear merino wool light hiking socks outdoors, hiking or for field work. Keep my feet dry and blister-free, and my feet never feel too hot. And they are super soft and itch-free. Light hiking socks work great all year round, if your feet get especially cold you can go medium weight for winter.

The REI brand is cheaper than Smartwool, and more durable in my experience. I was going through Smartwool socks really fast, always wearing out the area around the Achilles tendon. Once I switched to the comparable model in REI house brand, they last for years without wearing out.

no, just keep using your sports socks if you are happy with them.I always take my HiTec walking socks with me as I do a bit of hiking,I have no idea what they are made of but they are comfortable in most walking conditions. for general touring and walking about I buy several pairs of really cheap socks (ie 5 pairs for £2.50) and throw them away after I have used them. might wash them once.

if it is warmer weather I usually have my hiking sandals and no socks.

Darn Tough's...........good from the streets of New York to the top of the Alps and everywhere between. Guaranteed for life and worth every penny. Once you become a convert you'll never settle for anything less...like Smartwool etc. Buy a couple different weights.

Costco! Kirand brand merino wool blend trail socks, 6 pair for $18 (men) or $20 (women) -- wear them all year except for sandal season.

Unlike cotton socks, these dry soft and comfortable.

We love Darn Tough. Smartwool wears out, so I bought a pair of Darn Tough. My wife stole them. Bought enough for a week and my wife stole them. Bought her some, now my socks have returned. My feet sweat very bad. With Darn Tough, they stay dry with no blisters or problems.

Wright socks. They are double layer and prevent blisters. Available at REI. When we packed to move to Europe, I ditched all socks except for these, black, white, den8m and taupe. They dry overnight!

Different brands/models of merino wool socks are made with varying percentages of merino wool. I prefer the high merino content versions, realizing they may wear out a bit sooner...but that's many miles of walking. Happy feet.