Why home prices have a season
Home prices are not the same in March and December. There is a real, repeating seasonal pattern, and knowing it keeps you from reading normal noise as a trend in your own number.
The spring and summer peak
Buyers and listings both surge from spring into early summer. Families move around the school calendar, homes show better in long daylight, and more competition tends to lift sale prices. By late fall activity thins and prices soften. The pattern is remarkably consistent from year to year.
Part of it is a mix effect
Some of the seasonal swing is not the same house changing value, it is a different mix of houses selling. Larger, nicer homes disproportionately sell in spring, which pulls the average sale price up without any single home being worth more. That is why a raw local median looks more seasonal than the market really is.
How a good index handles it
A repeat-sales index like the FHFA series compares each home to its own earlier sale, which removes the mix effect, and the series is handled so a spring bump is not counted as real appreciation. That is one reason to trust an index trend over a raw median. How the index works.
What it means for your number
Do not read a strong spring or a soft winter as your home gaining or losing real value. Compare like periods, year over year, and watch the direction across several quarters rather than reacting to any single one.