least for some minutes to hours. For example, during the night from the 6th to the 7th of February 2012 (see Fig. \[fig:IFArecord\]), up to 13.99 were recorded at 10:30 p.m. This spectacularly bright value corresponds to a luminance of 0.27 or 1570 times the natural zenithal sky brightness. In this case, which typically occurs when there is snow cover and ongoing snow fall, the diffuse backscattered light from the sky alone would illuminate a landscape with more than 1lx. Under such conditions, one could even consider dimming down or switching off local illuminations of small streets and paths, since any landscape which is uniformly illuminated at 1lx appears brighter than the same landscape with “punctual” illuminations even at peak values of several lux.

![During the night from February 6th to February 7th 2012, the NSB reached a peak value corresponding to 0.27 or 1570 times the natural zenithal sky brightness.[]{data-label="fig:IFArecord"}](Figure6.eps){width="10.5cm"}

Special cases: thunderstorms, New Year’s Eve
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Our NSB measurements not only show the strong influence of lighting, but also the strong (but short-term) influence of lightning. Given that thunderstorms occur much more frequently during the summer months in Austria, the detection rate of lightning is highest between June 