Temperatures are no very high in many parts of the world. Riding in this conditions also represents some danger as it can be difficult to pay attention to everything while you're sweating and feel tired. We all fall into the temptation and ride without protecting gear to refresh our bodies, and that's okay for a short ride, but riding in all weather conditions imply some effort, and not to avoid protection.
My first advice is to keep yourself hidrated. Make as many stops as you need and drink enough water to keep yourself alright. When we haven't drunk enough, we feel tired and a bit angry before we really start feeling bad and even before thirst appears. Drink regularly during your rides, I always get an isotonic drink as my preferred solution.
Do not avoid your protective gear. If the heat is too much for you, you can get some summer staff that allows wind to get inside and cool yourself. I don't have that staff but I leave zippers on my chest and wrists open and get a similar effect. You can use sunglasses and lift up the helmet visor as well. Once you get rolling, temperature falls. Traffic lights are a nightmare, but they alway are, aren't they?
If you have the change, rest near a lake, river, beach or anywhere you can swim. Nothing better than stripping in the middle of the forest and jumping naked into a river, you'll be a new person after that, I can tell you.
Remember the heat is good for your tyres' grip and to get the engine rolling properly, but check the engine's temperature as too much temperature can cause damage to it and it can become into a smoking stopped bike. This is specially for those you ride classic bikes, like me.
Enjoy your ride, no matter how hot, cold, windy or horrible the weather is. Bikers are bond to all weather conditions.