National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI)
The U.S. Climate Reference Network (USCRN) is a systematic and sustained network of climate monitoring stations with sites across the conterminous U.S., Alaska, and Hawaii. These stations use high-quality instruments to measure temperature, precipitation, wind speed, soil conditions, and more. Information is available on what is measured and the USCRN station instruments.
As for soil temperature and soil moisture, USCRN offers monthly, daily, and hourly observations taken at the depths of 5, 10, 20, 50, and 100 cm.