Naples and Pompeii

I suspect you would not enjoy it in mid July. I was there in late October and it was pleasantly warm. I would not go there in July even if someone paid it for me. In the worst case scenario that you find yourself there in mid July, do some light sightseeing early morning and spend a day on the beach (locals can advise you) in the shade.

Go early or go late but don't go mid-day. Pompeii has no shade -- it is wide open. There is luggage storage at the entrance and you hire a guide at the same location. Might be able to join a group and share the expense. Naples is great especially the museum that holds all of the materials recovered from Pompeii. I think it is a must see and gives greater meaning to Pompeii. I am not a big fan of Vesuvla. Just a big hole in the ground with steam and smoke.

Yes it will be hot but go if that is what you want to see and do. I just about died with the heat there last summer but I made it and enjoyed my visit. An umbrella can shade you from the sun and offer a little break.

If you are returning to Naples from Pompeii it's probably better to leave your stuff in the Naples train station than schlepping it on the local Circumvesuviana train. The National Archaelogy Museum in Naples is a wow. The RS guide has an interesting self-guided walking tour of Naples. I would want to be in Pompeii when it opens, before it gets really hot. 2-4pm is probably the worst.

Realize that Pompeii is a city, and a spread-out city at that, with no high-rises (rather like Los Angeles, come to think of it). So, to visit Pompeii involves a lot of walking. More so if you take the time to see the Villa dei Misteri, which IMO is well worth the effort -- the frescoes, the garden, and the building are so beautiful!
http://pompeiisites.org/en/pompeii-map/

Get yourself a guide for the day. Ours picked us up at our hotel in Naples first thing in the morning., much cooler at that time of day. His discussions at Pompeii and in the afternoon the museum were spot on. Our guide was also a professor at the University of Naples.

What is there to do in Naples? Is it worth going and spending the
afternoon/evening?

Consult the Blue Guide or a website like Napoli Unplugged. You won't have time to see much--it would take weeks!

What is there to do in Naples? Is it worth going and spending the
afternoon/evening?

I would pick up a guidebook from the library that covers Naples. There is more to do there than a simple afternoon. World class archeological museum, beautiful and ornate churches, Veiled Christ sculpture in the Capella Sansevero, Certosa di Martino monastery on top of the hill with great view of the Bay of Naples, great food, and authentic local feel (not scrubbed for tourists), to name a few. I wouldn't skip it but if you give it such short shrift, then it's probably not worth going since it will just stress you out. It's a bit intense to say the least. It will be crazy hot in July (especially in Pompeii, without a lot of shade) so prepare.

We only went to Naples to see the Archaeological Museum with artifacts taken from Pompeii. To get the most out of your tour of Pompeii, we would highly recommend this as a must do in Naples. Like everyone has pointed out, the scavi sight is massive with almost no shade. During the summer you should probably wear a hat and bring a water bottle. There are still working fountains to refill your water bottle.

Naples is definitely worth seeing and a night there would suit you. I would splurge a little on a good hotel in the city center, you won’t find it touristy. If time is an issue, Herculaneum is a great option over Pompeii. It is smaller, but just as fascinating and in some ways better than Pompeii. It is much closer to Naples and is open quite late in the summer. I’d imagine this: a morning ferry to Naples from Ischia, check in to you hotel (or leave luggage), explore Naples (Archeological Museum is an absolute must) and see Herculaneum late in the day when it’s cooling off. That’s pretty doable.