Does the obligation to use low-beam lights in the car apply only to the winter period?

Why?

The requirement to use dipped headlights applies throughout the year, not just in winter. Between dawn and dusk, daytime running lights may replace them when visibility is not reduced by weather or other atmospheric conditions. The green symbol with sloping beams in the image represents dipped headlights.

art. 51 ust. 1 i 2 Prawa o ruchu drogowym