Testes position is temperature dependent for better and adequate spermatogenesis. In winter will go more frequently into tummy. In summer mostly stay outside. So during summer scrotum( testicular sac) appears more lengthier than penile size.. Any now needs to look for many clinical conditions like...hydrocele ,hernia, torsion,pubertal progression etc... So need to measure testicular size and volume. Take pediatric Endocrinologist opinion

Yes get a usg testis and inguanal region to rule out hernia and hydrocele show to a pediatrician