Seasonality

Part of it is the audience: school terms, holidays, weather, tax deadlines, whatever drives people to search for your topic. Part of it is advertisers, whose budgets do not spend evenly across twelve months. The practical trap is comparing this month with last month and reading a normal seasonal dip as decline. Look at a 90-day window first, then a multi-year one, so you can see whether the same shape appeared at the same point in previous years before concluding anything is wrong. Once you know your channel's pattern you can plan around it, banking work ahead of the quiet stretch and publishing the big ideas into the busy one.