Global Navigation Satellite Systems (GNSS) are vulnerable to extreme G5-class geomagnetic storms, but their influencing modern infrastructures like IGS and AUSPOS lacks detailed empirical assessment. The author assesses the impact of the May 11, 2024, G5 storm on static GNSS measurement accuracy quantitatively. Using data from some 300 IGS stations processed by the AUSPOS service, we compared the accuracy on the storm day to that on a geomagnetically calm one (May 20, 2024), analyzing 3D, planimetric, and elevation errors with the Mann-Whitney U test. The storm caused a statistically significant (p < 0,001) negative effect, with median 3D, planimetric, and elevation errors increasing by 23,5; 14,3, and 20 per cent, respectively. The greatest deterioration affected the 3D and altitude components, with error interquartile ranges growing by up to 50 per cent. The spatial distribution of errors was global yet heterogeneous, worsening notably in high-latitude regions. These results are critical for risk assessment in high-precision applications like land- and mine surveys, confirming the need to account for space weather factors in GNSS work