The Meseta is always beautiful. It can be cold or hot, wet or dry, windy or still. It is always largely solitary and allows for a good amount of contemplation, prayer and meditation.
While the terrain is flat to gently rolling, and there is not a lot out there, many folks including me, find it entrancing. There is a lot of commercial agriculture and the crops vary from month to month.
In October, the harvest should be over, so the fields will likely be brown and dormant, getting ready for winter. That, to me, looks like the setting for an impressionist painting. Others have addressed the weather so I will not.
In the winter, expect to see brown mud, snow covered fields, or possibly some grass crop grown as winter cover.
In the spring, there is an explosion of color as flowers and crops sprout from the earth. This is my favorite time to walk as I enjoy the colorful flowers, growing green fields, new animals, and the weather in general. Spring is a time for new birth, and it reaffirms my reasons for doing a Camino.
During the summer months, June to September, the Meseta can be VERY hot and dry. This happens to be the most popular time of the year. This is not because the Meseta necessarily has a lot to offer, but because that is the time of year when most pilgrims can take the time to walk a Camino, including the Meseta.
Hope this helps.