Inside the CRS, a maximum/minimum thermometer set on townsend support can be found, used to record high and low temperatures daily. The accuracy of the maximum and minimum thermometers is ±0.3°F above freezing and is read to the nearest whole degree. Generally, the maximum and minimum thermometers are within a degree of each other.
Many official COOP sites still use the CRS but are slowly being phased out in favor of the more modern Maximum Minimum Temperature System or Shelter, or simply, MMTS. The MMTS is much smaller and contains an electronic sensor connected to a readout display that indicates the temperature. Liquid in glass thermometers will far outlast their electronic counterparts and never change, unlike the electronic versions that can introduce subtle inconsistencies in the temperature data. Mercury or liquid in glass (LIG) retain their original calibration, unless the liquid separates or the thermometer gets broken. The LIG does not require a source of electricity.
The data on this site is raw or observed temperature data as recorded daily. Meaning there are no adjustments made to the temperatures. What the thermometer reads is what is recorded. The 24-hour maximum temperature may be higher at times due to the fact that the shelter is located in my backyard near the city. On a hot summer day with full sun, the maximum temperature may be 2 to 3 degrees higher than the official temperatures that are taken in the open on the outskirts of the city. However, the temperature is correct for the location and exposure and is negligible. The observation temperature and minimum temperature will be less affected by the location.