I think the key word in this sentence is
tolerate. The snake may
tolerate it, but that doesn't mean it's comfortable for them. When it gets hot in the summer, it doesn't harm or kill me, but the heat makes me feel uncomfortable. :shrugs: A thermostat ensures your snake stays safe and comfortable, and heat sources get extremely hot. I've seen reptile heaters, uncontrolled, reach temperatures of more than 120F.
To answer the original question - what are the temps with and without the lamp? Still, I would recommend you invest in some type of control for the lamp. IMO it's more or less essential. Good luck!