Leather offers the best protection by a considerable margin. It is tough stuff, and when worn as a tall bootalong with loose jeans or other long pants that can snag a rattlers fang before it snags youoffers excellent snake-bite protection. Most rattlers in your area, such as the Western Prairie Rattlesnake and the Rock Rattlesnake, are relatively small (up to three feet or so), and so have fangs that arent really up to poking through much leather. The exception is the big Western Diamondback, a snake that can hit six feet and sports fangs to match. Its also one of the most common snakes.
But I understand your point about heat and leather. Fabric bootsagain, worn with some kind of long pants or snake chapsoffer reasonable protection if worn as a tall boot, not a short light-hiker. You need to protect from the knees down in some fashion, and from mid-shin down with something thicker, such as boot leather or boot fabric.
Keep in mind that rattlers really dont want to hunt" you. Theyre after small mammals, and would rather you just left them alone. Hence the rattles. But when scuffling through brush or rocky country, you always risk stepping on a snake or coming close enough for one to strike, especially in the after-sunset hours when theyre most likely to be active (in the heat of the day most reptiles look for shade and hunker down). And people tend to try to corner snakes, causing the snake to bluff and crawl toward the intruder. Again, it would much rather you just left than risk taking on such an obviously large opponent.
One data point to consider: A poisonous snake can strike accurately to only about a third of its body length. So a big (six foot) snake can hit you from about two feet away. Maybe a bit further, but that would depend on its aim and a little luck.
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