Transcranial Doppler sonography was used to study the developmental dynamics and seasonal variation in cerebral blood flow in 95 middle school students aged 7–18 years, natives of Arkhangelsk District. Results obtained from long-term (2005–2014) monitoring of schoolchildren are presented. Linear blood flow velocity (LBF) was found to decrease gradually from junior to senior school age, mean levels in the middle cerebral artery were lower and those in the basilar arteries were higher than normal for the mid latitudes. The influence of the seasonal factor was greater in children of the younger (in boys) and intermediate (in girls) age groups and disappeared in the older group. The largest seasonal variations in LBF were seen in the arteries of the carotid basin and the most constant LBF was seen in the basilar artery. Assessment of the index of resistivity of circulatory resistance in schoolchildren of the younger and intermediate age groups decreased in the arteries of the carotid basin in spring and summer and in the basin of the posterior cerebral artery in winter. Levels of LBF variability identified groups of children with different levels of “sensitivity” to the effects of the seasonal factor.