Late on Sunday night, wildfires began tearing through Northern California. By Monday afternoon, 14 major fires burned throughout the state, according to Cal Fire. As of Wednesday, more than 20 fires are burning in Northern California over 170,000 acres.
Red spots indicate active "hot spots" that MODIS has detected within the 6 hours. They are not necessarily fires. See below for more on how this map is generated.
You can click on the arrow to select, or deselect, different map layers. Use the plus and minus to zoom. The map covers fires throughout the state -- you can drag to change the area. The map autoupdates as MODIS does, which can take 2 to 4 hours from when the satellites record the hot spots.
NASA uses satellites to detect fires. The instrument aboard satellites, known as MODIS (Moderate Resolution Imaging Spectroradiometer), can "see" hot spots because fires produce a recognizable type of heat. Whenever satellites detect a hot spot, they flag the signal's location and add it to a dataset. An algorithm works with the data and can detect a fire about the size of a quarter-acre. There are two satellites orbiting the earth every 98 minutes. Then that information then goes through an algorithm and is sent back about every 2 to 4 hours.
Fire perimeter data is from Cal Fire and Cal OES.