The constellation Cassiopeia is visible year-round from the Northern Hemisphere. However, it's most prominent and easily recognizable in the fall and winter months (September to March).

Here's why:

* Position: Cassiopeia is a circumpolar constellation, meaning it never sets below the horizon for viewers in the Northern Hemisphere.

* Visibility: During the fall and winter, the constellation is positioned high in the sky during the evening hours, making it easier to see. It's especially noticeable in the northern sky, forming a distinctive "W" shape.

While Cassiopeia is technically visible all year, it may be obscured by the Sun's glare during the summer months or appear low on the horizon, making it harder to spot.