From an Intro Post by Dr. Jeff Masters’, Weather Underground’s Co-Founder:
The Record Extremes page will give you the option to see U.S. and international records on a map and table. You can select any combination of record types at once, which, combined with the map, provides a interesting visual way to investigate record-setting events. The product uses data from three sources: (1) NOAA’s National Climate Data Center, (2) Wunderground’s U.S. records, and (3) Wunderground’s International records.
The NCDC records begin in 1850 and include official NOAA record extreme events for ASOS and COOP weather stations in all 50 U.S. states as well as Puerto Rico, the Virgin Islands, and the Pacific Islands. In this database you can find records for maximum high temps, minimum high temps, maximum low temps, minimum high temps, snow, and precipitation on daily, monthly, and all-time scales.
The Wunderground extremes were compiled by our weather historian Christopher C. Burt. Chris monitors 300 stations across the U.S. for Record Extremes in maximum and minimum temperature, precipitation, and snow events. Most of these U.S. records go back to the end of the 19th century, though the oldest site in this database is Charleston, SC, where precipitation records started in 1737! Internationally, Chris monitors 150 countries worldwide for all-time record high temperatures and all-time record low temperatures. If you’re interested in diving deeper into extreme weather in the U.S. and abroad, Chris’s book Extreme Weather is an excellent resource.
Direct to Weather Extremes