Seasonality is the set of predictable, calendar-driven cycles that move mobile growth metrics across the year — install demand, ad costs ([[cpm]] / [[cpi]]), and conversion all rise and fall on recurring patterns. It operates at two levels: market-wide (the whole auction gets more expensive at certain times) and category-specific (your vertical has its own demand calendar).
The two layers of seasonality
- Market-wide auction pressure — Q4 (Black Friday through the holidays) is the universal spike: e-commerce and brand advertisers flood ad inventory, driving CPMs up for everyone, including non-retail apps competing in the same auctions.
- Category demand peaks — fitness and health apps surge in January (resolutions), travel apps in spring/summer, education at back-to-school, shopping in Q4, tax apps in Q1.
- Weekly + daily cycles — install behavior and conversion vary by day-of-week and time-of-day too, a micro-seasonality layer on top of the annual one.
Planning around it: seasonality changes blended [[cac]] enough that timing is a real lever. Pull spend forward into cheaper windows where your LTV math still works, lean into your category's natural demand peak with extra budget and seasonal creative, and avoid scaling into Q4's expensive auction unless your own seasonal demand justifies the higher costs. The mistake is treating UA efficiency as constant across the year — it isn't.