Most white people are not able to get a proper strong tan. And even when they do it compares to SPF 5, which is not nearly enough to protect you from working in the field for the entire day.
So, yeah, you’ll have a tanned neck, but also it will be red very, very often.
You’re running it too cold. I have the same if I set it to 21/22 celcius. Set it to 24/25. That’s still amazing in summer and yet no sore throat or getting sick.