Nederbördnormaler

Nederbördnormaler, or precipitation normals, are long-term climate normals that describe typical precipitation patterns for a location. They are usually defined as 30-year averages of precipitation measurements and serve as reference values for comparing current conditions with what is considered normal.

The concept is part of the broader system of climate normals established by international meteorological practice. Normal values can be provided for different temporal aggregations, such as monthly, seasonal, or yearly totals, and may distinguish between types of precipitation (e.g., rain versus snow) in some datasets. They are derived from historical observations from a network of weather stations, after quality control, homogenization to remove non-climatic breaks, and gap filling where data are missing. The result is a set of typical values for each location and time period.

Nederbördnormaler are used in weather forecasting and climate analysis to identify anomalies and trends. They inform water management, agriculture, infrastructure planning, and risk assessment by indicating how current precipitation compares with what is expected for the period. They also facilitate communication of climate variability to the public and policymakers.

Update cycle and regional differences: the standard 30-year interval is periodically revised to reflect recent climate conditions. Historically many regions used 1961–1990 normals, with updates such as 1991–2020. Different countries and organizations may publish updated normals on their own schedules, and some provide both old and new normals for comparison.

Limitations: normals are descriptive, not predictive. They summarize past climate, and their relevance can change as climate variability and long-term trends shift precipitation patterns. Regular updates help maintain their usefulness for interpretation and planning. In countries like Sweden, national meteorological agencies publish nederbördnormaler as part of their climatological products.