Sure, but in the novel, Arrakis really is hot. In the Appendix, it's stated that the sand surface reached 76.85 Celsius (170.33 F).

Sand surface =/= ambient temperature, with all the research that went into Dune, I think Herbert was aware of that

[sigh]. You could have just googled this, but from the Appendix:

> He found that in the wide belt contained by the 70-degree lines, north and south, temperatures for thousands of years hadn't gone outside the 254-332 degrees (absolute) range

That's -2 F to 137 F in the arctic circle.

> Kynes and his people turned their attention from these great relationships and focused now on micro-ecology. First, the climate: the sand surface often reached temperatures of 344° to 350° (absolute). A foot below ground it might be 55° cooler; a foot above ground, 25° cooler.

That's 114 to 125 degrees Fahrenheit for "a foot above ground".

So once again, yes, very hot.