Weather instruments are used to take measurements of various atmospheric parameters at local weather stations.
1.10b Averages and Normals
Average weather and climate conditions describe the expected weather a location is likely to get. Normal conditions describe what is normal for an area using the most recent statistically adjusted 30-year interval of the average weather conditions.
Extremes of weather describe the range of possible weather and climate conditions that you can expect to encounter at your location. These can be expressed in a variety of ways, from the highest or lowest temperature ever reported at a site to a probability of occurrence for rare events like heavy rainstorms.
Trends in climate can be caused by natural changes or variability in ocean currents, land use, solar radiation, or other factors. They can also be the result of manmade influences on climate. While some trends in climate variables reflect local changes in climate at a single location, trends across regions and the globe indicate significant movements away from "average" conditions which could cause disruptions in society and global ecosystems.