How should I work out over the summer?

Try tibatas! They'll really work you and they'll bring down your erg time significantly if you keep up with it. On an erg, do something like 50 seconds on with full power, full speed. 10 seconds off at a paddle. Do it about 10ish times to make one full workout. There is a girl at out boat house that does these once in the morning, twice in the afternoon, and she just became the fastest single in the southeast. So try it out!