Charade No. 3 (from the Austen family)

Here is a charade by Jane Austen's brother, Francis William Austen.

By my first you may travel
      with safety and speed,
Though many dislike
      the conveyance indeed;
My second no woman can well be.
My whole takes a change
      several times in a year;
Hot and cold, wet and dry,
      benignant, severe.
What am I, fair lady, pray tell me?