I spotted these clouds yesterday afternoon. Cirrus are very high - over 5km up in the atmosphere. It might be below -20 degrees Celsius up there. Thus they are made of ice crystals rather than water droplets. The winds are very strong at that height so the clouds are strung out and are shaped like commas. They form ahead of a warm front. Oncoming warm air is pushed up above colder air and condensation happened. The front arrived overnight. It did feel like a warm night to me.
