You don't have a lot of time before xc, so you should start to build a base, without worrying to much about actual workouts. Will this be your first year running? How much have you been doing? Run at 5 days per week, if you are just starting, and work up the length of your runs. If you could run 40 mins a day for one week, then the next week, change one of those into 60 min. The next week, increase 2 of your runs to 50 min. Basically, keep building up in that way, till the start of the season, so you go in with plenty aerobic power. Do 8-10 100m strides 2-3 times a week after your runs.
Do 5-8 mins of abs everyday! < This is VERY important.
As for the long offseason, there are multiple options. If you lived in the northern states, I would suggest forgetting about running for the winter months, and forcing yourself into Nordic skiing. It is very beneficial towards you aerobic power...perhaps even more so than running. Ben True Skied, and look how he's ended up, and how successful he was in High School.
If you don't live in a Northern state with the skiing option, then you'll have to gut it out yourself. I'm sure the people on your team, if they are serious, do training runs on the offseason. If they don't throw out the idea for all of you to meet during the offseason at place x at time y.
If you have dedication, this offseason could make you a better runner than if you had a season. Without meets, you are able to run 3 HARD workouts a week, and get into TREMENDOUS shape.
Hope this helped a wee but! Good luck!