I wasin Cadiz in December. Unusually high temperatures. 18-21 celsius, No rain. You will probably have 16-18 celsius with occasional showers (I mean SHOWERS) but many sunny days. You will be tempted to jump in the water at at the long beach in Playa de la Victoria or just sit around at the small beach in old town; Playa de la Caleta. Recomended trip