Translation:However, it is cold today.
でも used at the beginning of a sentence is mainly verbal. しかし can be used written or verbally.
There is very slight difference. でも is relatively less strong thanしかし. でも is close to Even So. You raise an exception while acknowledging a general case. しかし is more close to However. You tend to raise an opposition.
Also, でも can be used to start a sentence, and しかし is used exclusively mid sentence