The weather in Iceland can be very difficult to predict. Sometimes the weather forecast shows one thing and you actually get a completely different thing. But with the time, the Icelandic Meteoservice has drastically improved. If you check the forecast, you can prepare yourself for that kind of predicted weather, it is sometimes slightly of the time frame, but you can get the idea of the weather for the next couple of hours.
I have checked the weather on Friday and saw that Saturday will be a very sunny and beautiful day. I packed my sunglasses (did not need them for a while now) and my gear and off I went on a January South Coast tour. And it was beautiful. Not exactly a good weather for taking landscape pictures as the sky was nearly completely clear. The best weather for Iceland and taking pictures is still the "Partially Cloudy". But the winter sun offers a special kind of light that you can see in the pictures.