Sunflower oil reaching smoke point on medium temperature. Is this normal?

I assume you're cooking steak when you say "meat." Cooking steak to a safe temperature isn't just related to the temperature of your pan. It's also related to how long you cook it and what cooking method you use. If you use a really hot pan for the entire time your steak will be overcooked on the outside by the time the inside is medium rare (save for thin cuts of meat).

When you sear meat you want to do it on a really high temperature for a short amount of time (just long enough to develop the crust) to maximize browning and minimize the gray bar between the outside of the meat and the inside, which is normally cooked medium rare. Some smoking of oil is normal at this high temperature. However, be careful not to leave the oil at too high a temperature for too long or it will catch on fire.

Note: it's best to keep a lid that fits the pan close at hand along with a towel or pot holder. If the pan catches on fire, do not panic! Immediately cover the pan with the lid and then take it off the heat. Bring the lid toward the pan from the side at an angle (shielding your hand from the flame) and then cover completely.

There are many methods for cooking steak in a pan. Some people sear in cast iron and then put the pan and steak in an oven to finish more gently. Some cook in the oven first then finish in a hot pan (this is called reverse searing). The advantage to this method is that the outside of the meat is dry and already hot so it will brown better and faster.

Sunflower oil has a relatively high smoke point (450°F), so it's a good oil to use.