Venemous snakes come in enough variety of types and sizes that most boots probably provide some partial protection. The venom of a baby rattlesnake for instance

Venemous snakes come in enough variety of types and sizes that most boots probably provide some partial protection. The venom of a baby rattlesnake for instance is much more potent than that of an adult; footware that can only stop small fangs would still be helpful. Snakes are almost never aggressive though. A significant portion of snake bites happen to drunk people being stupid. The general guidance is to avoid putting your limbs anywhere you can't see and to leave snakes alone when you encounter them.