As far as the heat goes, you just get used to it. Light and loose clothing and doing the midday siesta helps a lot!
I have used a similar product to the carrots you described, though mine were home made, and was told to fill them with pea gravel to stop the seep holes getting clogged. They are a handy way to provide constant water. In the south of Italy, where my in-laws live, people use pieces of drainpipe - 4 inch diameter, driven 4 feet into the ground, to water in new olive trees or grape vines for the first two to 4 years. Just go along with a hose (or buckets, which isn’t too good for the back!) and fill up each pipe.
Have you thought of using tree branches for your climbers? They look very nice, especially for peas or sweetpeas, and can be had for free from most people.
Yes, I've been saving my white birch bark branches, but they aren't tall enough or strong enough. But reinforced with skinny rebar, maybe I could make something attractive with those. I never thought of using rebar to make them tall enough; they'd cover them in no time. And I'm not as creative as some what I've seen on the web.
No nice straight branches for me, have to go to some woods to find some strong enough.
I'll see what I can put together with that this winter. Thanks for clarifying my thoughts.
I might just use the gallon jugs again. When all is said and done, I think they're easier than the carrots. Only drawback is they don't deliver water down deep.