I lived in Tampa for a few years and experience most of the same issues you mention. Here are a few tips to mitigate them.
- Run early in the morning. Yeah, this ones pretty obvious. It’s cooler in the morning.
- Run at night. It’s still a bit warmer than the morning but at least the sun doesn’t bake you.
- Run immediately after thunderstorms. You can set your watch to afternoon thunderstorms in Florida. After the front passes the temperature will drop a 5-10 degrees and the humidity will drop a bit. Watch the radar and take advantage of this.
- Run near the coast. It’s usually a few degrees cooler and has a nice breeze.
- Find parking garages. I did most of my hill work in multi-story parking garages. It’s the next best thing to a real hill.
- Run bridges. Like parking garages, they double as a hill. The disadvantage is that they offer no protection from the sun.
- Long intervals in subdivisions. Subdivisions are ubiquitous in FL and they usually have well paved roads, light and slow moving traffic, and offer tons of loop options. Mark out a few .5mile to 2mile loops and do your long interval work there.
- Embrace the heat. If you can’t avoid it you might as well learn to thrive in it. Take comfort in the fact that if you can knock out a hard workout or long run at 3pm on a still day in August you can handle any weather condition Mother Nature will throw at you.