This section shows how observed values deviate from the 30-year normals (long-term averages). The pre-calculated maps are for your convenience; you could obtain the same results by comparing datasets available on the "Normals" tab with the appropriate time-series data available on the other tabs. The maps show the deviations (commonly called anomalies) of average min/max/mean temperature or total precipitation from the average/total represented by the 30-year normals (1981-2010). Maps are available for each month and year since 1981, plus the most recently completed three quarters.
The calculations use as many as possible of the station networks and data sources ingested by the PRISM Climate Group, not just those that have existed for long periods of time. See PRISM datasets for more information; the data available from this page is "AN81m" (monthly). For information on when the grids were most recently updated, see calendar of PRISM data updates.
Results for dates >6 months old should be considered "stable" (unlikely to change until a major version change). Those for more recent dates should be considered "provisional" (still likely to change as reporting stations finalize their information).
|Download size:||approx. 1MB per full-size image|
|Climate variable:||precipitation||mean temperature||minimum temperature||maximum temperature|
|Temporal period:||monthly comparisons|
|quarterly comparisons||January – March (2017)|