Here's a tip.
Point the overflow tube from your expansion tank out under the side of the hood. Then, if the car overheats to the point that the expansion tank is full, it will start spraying water on to the passenger side of your windshield. It's easy to miss a temp gauge reading but it's almost impossible to miss water spraying all over your windshield.
Keep going after that, Safety will be putting down speedy dry and/or picking up pieces from your engine.
220 isn't good.
J~
That's what we do in the stock cars. Didn't think about doing it in the Miata, good call. For the stockers we run a different temp range so when it's just spritzing, usually prior to the idiot light or danger zone on the gauge, it means keep an eye on your temps. Not uncommon to squirt a few times during a race. OTOH, if it pees out, time to park. I've seen the tube save an engine or two.