When we refer to current conditions being “warmer than normal” (or colder, or wetter, or drier, or…), we compare current conditions to averages over a 30 year climatological reference period, i.e. the statistical normal. The most recent reference period is 1991-2020. As the reference periods change, so does the statistical normal and the anomalies or “departures from normal” that we calculate based on the normal.