The Beaver Creek Fire in northern Colorado on June 21, 2016.
PlanetScope image ©2016 Planet Labs, Inc. cc-by-sa 4.0.

This post from the earth observation satellite company Planet (formerly Planet Labs) describes the use of satellite imagery to monitor forest wildfires and to help prevent them from happening: Fire Watch: Watching and Understanding Wildfires from Space — Planet Stories — Medium –

Satellite imagery has long played an important role in fighting wildfires, from estimating the amount of dry vegetation available to fuel a fire to evaluating the severity of a burn in the wake of a blaze. The rapid revisit rates and relatively high resolution of Planet’s RapidEye and Dove instruments allow unique ways of preparing for, monitoring, and responding to fires.

True-color image and vegetation map of the
site of the San Gabriel Complex fires on June 4.
RapidEye satellite images ©2016 Planet Labs, Inc. cc-by-sa 4.0.

These images show the site of the San Gabriel Complex fires, which ravaged the mountains north of Los Angeles. Starting on June 20, 2016, the Reservoir Fire and Fish Fire consumed a total of 9652 acres, before being contained about a week later.

On the [top] is a true-color image, showing the area On June 4, 2016, more or less as it would appear to a human observer. The dark green, chaparral-covered hillsides contrast with gray rooftops and roadways — the northern fringes of the Los Angeles conurbation.

On the [bottom] is a map of Normalized Difference Vegetation Index (NDVI), a measure of plant health and abundance. Dark green represents thick, vigorous plant cover, while lighter greens represent thinner and less healthy vegetation. Beige areas are vegetation free — bare soil, rock, asphalt, or concrete.

Vegetation Index maps are a valuable fire-fighting tool because they show fuel available to feed a fire. This can help land managers plan efforts to thin vegetation on vulnerable land to limit the intensity of damaging fires, or prevent them from spreading in the first place.

True-color and near-infrared false-color images
of the San Gabriel Complex fires on June 22, 2016.
RapidEye satellite images ©2016 Planet Labs, Inc. cc-by-sa 4.0. 

True-color and near-infrared false-color views of the San Gabriel Complex fires show the extent of the blazes on June 22. In true-color ([top]), smoke is blue-brown, burned areas are dark gray, and flame retardant foam laid down in front of advancing flames is bright red. In false-color ([bottom]), the smoke almost disappears, leaving a clear view of the burn scar. More severely burned areas are darker. Vegetation appears bright red, and water is dark blue.

Satellite images can help fire fighters during a fire outbreak:

Up-to-date vegetation data can help predict the propagation of a fire, especially when combined with additional information like topographic maps, weather data, and land cover classification. This allows firefighters to efficiently combat wildfires and protect at-risk property.

And after a fire the satellite information can help with rehabilitation of the affected areas:

The USDA Forest service employs Burned Area Emergency Response teams to evaluate the severity of fires, and quickly rehabilitate areas vulnerable to threats like erosion and the spread of invasive species.

New low cost smallsat constellations like that of Planet’s can provide more frequent images of a fire area, in some case multiple views per day, and are making space imagery more accessible and affordable.