Effect of Sunlight on hair grafts

I am planning to get a facial hair/hair transplant in March. I don't work a physically demanding job, so was planning to take the day off the procedure off and the following day, and to head back to work on the third day.

I don't live in an area with super high UV exposure in March, but on days when it is sunny, the UV index can get up to 4-5. I don't plan on sunbathing any time, but know that sun exposure post-op should be avoided. I have an hour's commute to and from my job in total, and in the afternoon hours, I am exposed to sunlight through the car windows.

How would this affect the newly transplanted grafts? Would it prevent them from taking/establishing a new blood supply at all? I know it's recommended that patients stay out of the sun post-transplant, but most sources I can find say that the main reason that is recommended is because it can lead to increased scarring or hyperpigmentation. What is the actual effect of sunlight on the grafts themselves? Will it cause them to die?