Yes you will need to leave the northern areas like Glacier and Yellowstone [which doesn't fully open until late May -Mid June] until later in your trip. Even in California the snow in the Sierra's will still be thawing and roads like the spectacular Tioga Pass in Yosemite may not yet be open and the Rockies are likely to see snow. You need to bring layered clothing and prepare for some cold nights in the RV, although they are quite well equipped to deal with them.

The good thing about the loop trip other than the one way drop fees is that you can choose the start finish point that offers the best flight deals from your cruise end point to home. So you might be better off starting south and heading east. Once you have done some research and got some dots on the map we can help fill in the blanks, offer suggestions and answer any specific questions you may have.

We love the RV Lifestyle but take into consideration that it is not the 'cheap option' in the US, especially with a trip such as yours. By the time you add the mileage charges and high fuel consumption (8-10mpg) to the campground fees and rental costs it will be a lot more than a car and motels.