From my experience the socks will be fine for 0-20°C for higher temperatures they'll probably be a bit too warm.

I think they will be a tad too warm for those temperatures.

If I were you I'd buy the Defeet Wooleator, the thinnest merino socks available on the market.

I have never worn them in 30c but have found them ideal between 10-25c. The wool seems to keep you comfortable over a wide range of temperatures.

I wore a pair the other day in around 14c and thought they were lovely and comfy. However I would have thought that at 30c they might be too warm.
If the temps are 30c do you really need to wear any socks or could you go barefoot and save the socks for the cooler days?
Enjoy your tour.

I've found them suitable for every temperature I've encountered, from pretty much freezing up in to the mid 30s. I don't know how wool does it but it keeps you warm in the cold yet cool in the heat, so I can't see you having any issues with them.

I have only used them for 4-15'C so far, but I used them with a shoe cover so it might be ok for you in warmer weather without a shoecover. I get very cold feet and hands though. The pack says you can wear them in warmer weather because they "breathe"