You aren't the first to have this problem, and you won't be the last. Keep scanning this bulletin board and you'll read letters from lots of people who've been there.
Given the time of day, heat, humidity, and lack of water you consumed, it's not surprising that your run was uncomfortable. Is it possible for you to run earlier in the day? Is your favourite running route safe enough for you to run at dusk? If you must run in mid-day heat, at least carry water with you.
Running, especially distance running, is not an easy activity. (Would we do it if it were?) It's easier, however, when you do what you can to minimize the negatives.
I'd predict that if you run in cooler conditions, you'll enjoy yourself more and finish in better condition. Good luck!
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