Hydrocephalus patients complain about symptoms related to weather changes, especially changes in atmospheric pressure (pat). We aimed to determine which physical, physiological, and pathophysiological effects can explain this phenomenon. We hypothesized that intracranial pressure (ICP) is influenced by changes of intracranial blood volume caused by autoregulatory changes in arterial diameter as a reaction to changing levels of arterial CO2 partial pressure (paCO2) caused by changes in atmospheric pressure (pat). To test this hypothesis, we investigated the influence of pat on paCO2, and then assessed the influence of paCO2 on ICP by extrapolating data found in the literature. Using conservative assumptions, we found that a change of pat of about 50 hPa will result in a change in ICP of above 1.65 mmHg, which could explain the symptoms patients reported.