One technique I have used that can produce strikes in hot weather is twitching. During the heat of the day cast a floating crankbait into a shaded spot and, instead of a straight retrieve, just twitch the pole every 10 seconds or so in the shade. This will imitate a wounded bait fish and will stay in the fish's strike zone longer, which is usually necessary as fish's metabolism drops during the heat.
Also, waiting until sundown is a good time to use this technique when fish will become more active.
Also, waiting until sundown is a good time to use this technique when fish will become more active.