There are lots of early flowering Clematis that definitely deserves an acknowledgement.
Cirrhosa varieties, cartmanii types, alpina, macropetala, montana and armandii are all widely available.
Cirrhosa, cartmanii and armandii are evergreen varieties. The earliest to flower are the cirshosas. These are winter flowering rather than early spring.
Early flowering cirrhosa varieties like Wisley Cream, with lime green nodding flower heads (above.) Freckles has speckled spotted flowers and evergreen foliage (below.)
Jingle Bells (below) may not have come out in time for Christmas but it it certainly a very early flowerer.
Alpina varieties such as ‘Purple Rain’ and alpina 'Willy' (below)scramble beautifully through a hedge and flower effortlessly with little maintenance each spring, providing a profusion of little alpine flowers. Clematis x cartmanii Avalanche is another very successful early variety.
Suffice to say the colour is out there. There are some really good plants that are worth adding to your borders, often overlooked not being aware there is such early flowering climbers available. Adding early flowering clematis varieties allows early spring borders to become outstanding.