with 40's celsius I would only go up the cable cars, dont even think other wise.Plus your time is limited.
You will need 1/2 a day there.Take with you water, sun screen and a hat and you should take a guided tour , its very interesting
i enjoyed the hike up (and down) but not in midday. the cable car up is nice because you can really get a sense of the scenery without all the panting and heavy breathing. if you start about 45 minutes before sunrise, take the snake path up.
