Resources relating to the National Oceanic and Atmospheric Association (NOAA)
Real-time climate information, including trends and variability of Earth's climate.
Temperature, precipitation and drought products produced by NOAA.
State of the Climate reports released by NOAA on a monthly basis, including information related to climate on both global and national scales.
NOAA Climate Data Online (CDO)
NOAA's CDO portal provides users with free access to data and the ability to apply filters to search for specific data. An example of a search using the CDO portal can be seen here.
Resources relating to the Midwest Regional Climate Center (MRCC)
Other useful resources
Daily archive maintained by Weather Underground. Users can search for a specific site and view hourly data.