I'm sure it will be warmer on the weekend
Caerau,
Dont worry too much, a calendar ride is all about doing the ride whatever the weather.(as long as it's safe)
The Drfww was my 1st ride too, and it was much colder.
If the weather is less than perfect you will find that some riders will skip the official route and head up the A38 to Gloucester for instance.
So don't worry if you happen to be in a group that goes off route, on my 1st go I found myself cycling on the A48 dual carriageway all the way to Newport , must have been 30 of us - a long snake of flashing leds ...
You say you have already done Cardiff Bristol Cardiff in awful weather solo, so you will be fine on this ride for fitness etc.
There may be some in shorts with a route sheet stuffed in the leg grippers, brrr. There was last year.
Here is an alt route for getting out of Cardiff Gate and going through Newport,
http://goo.gl/maps/jWVHFYou may find yourself in a group that goes this way. Just a heads up.
And personally I might buy some food at the petrol station on my way out of Monmouth, in case the new cafe at Mitchel Troy doesnt have an "audax" menu.
from Newport to Cardiff I'll be on the A48 because its likely to be dark.
Cu at the start, Blue Ribble and my best aldi top.
Ian