I got a temperature raster (maximum temperature for January, global extent) and the value range seems to go beyond the valid range. The highest is 42.006 (which I assumed should be Celsius) but the lowest is -9999 (which corresponds to the ocean). The image is attached.
You are looking at a NoData value. Taken from the ArcGIS documentation:
Cell values can be either positive or negative, integer, or floating point. Cells can also have a NoData value to represent the absence of data. Sometimes there are homogeneous areas in a raster dataset that the you do not want to display. These can include borders, backgrounds, or other data considered to not have valid values. Sometimes these are expressed as NoData values, although other times they may have real values.
If you want to change the color for the NoData pixels you have to specify it in the symbology as follows:
In case the NoData value is not set go to ArcCatalog or the Catalog window -> Right click on the raster -> Properties and Edit the NoData value.