Worst 3 months of the year for sales/revenue, in this order:
1. April - tax season in the US.
2. September - back-to-school begins and summer cc bills come due.
3. August - everyone on holiday and spending on vacations.
And just to complete the Year:
A) Best months: Oct - Feb (the Holiday months)
B) March: up-and-down (many religious holidays, sporting/betting events, spring break, etc)
C) Back to "normal" months: May-July
Plan accordingly folks!
