I'm in the process of planning a trip to the Cordillera Blanca, and I was wondering what the weather on the mountains would be like. I'm planning on climbing Urus, Ishinca and Tocllaraju. How cold will it get?

Not particularly cold. On Toc, if you run hot, a 20 degree F down bag will work at night if you wear your puffy in your bag. A zero degree F bag is what you really want though. Top of the line boots for sure Spantik/Baruntse/Other and a variety of gloves and a good puffy jacket. Night time with a cold front will be in the teens or lower. When the sun comes up you can climb comfortably in a softshell with 1-2 layers beneath

Hi sharperblue, I have a Mountain Hardwear Ratio 15, rated to -4 C / 24F degrees (comfort). Would that be enough for trekking/camping in the CB in July or should I get a warmer bag?

This time I won't be mountaineering, would use the bag for the Santa Cruz trail and similar.

Thanks!

Sure; if it's just the Santa Cruz or huayhuash trek and no mountaineeeribg that will be more than adequate

Great, many thanks!

With regard to clothing/insulation, a light jacket like the thermoball, nano puff or similar (plus fleece, etc.) would be sufficient? Or is a more "bulky" down jacket recommended?

I would definitely recommend a heavier puffy, or a heavy inner as a supplement at least - the valley floors will get 2-4" of snow here and there and the mornings can be very cold. a decent marmot/MH jacket with 600 fill down (and lots of it) compresses down very small