I agree with what has already been posted. My regulars stay with me throughout the summer and my volume with them goes down slightly because almost everyone takes a vacation here or there. New leads slow down more than that.
The best way I’ve found to be busy in July and August is to market well in April and May to build up my client base so that when it naturally drops off over summer, I’ll still have a reasonable workload. This year, I wanted more time with my family so I didn’t shore up my business in April and May because I welcomed the natural drop after school gets out through the summer. But in past years, I’ve advertised my personal training and small-group classes really hard in Spring to have in and solid before summer. I also run group-ex contests and events during the summer to keep people interested, since a good portion of my training clients come from my group-ex classes.