My car saying "slow down"

What is your question?

Was driving my 09 lancer for about 1 hour on the interstate going about 70mph. Car was saying "slow down" Having to pull over and let it cool down. All fluids are full, was running the ac but turned it off and still did it. Temp outside was around 100 degrees could this have an effect? What could be the problem?? First time this has ever happend.