A problem I would pleasantly deal with almost on a daily basis during monsoons in Delhi, after getting off the school bus because the bus-stop was 150m away from home.
My answer is type of clothing is also a big factor.
It's a problem of vectors. A running boy is hit by a bigger resultant vector [vertical component (rain speed) + a larger horizontal component (running speed)] compared to a walking boy, who is hit by a much smaller resultant vector [same (rain speed) vertical component but a smaller horizontal component (waking)]. In that situation falling raindrops slide off the clothing for a walking boy easily as they are close to vertical, but are hitting and entering the clothing for a running boy as the angle is more favorable.
And believe me, as a kid I always wondered didn't I run fast enough because I'd keep getting wet even more each time 😅