At first glance, a storm appears to be rising behind this egret at the edge of Big Slough in the Brazoria Wildlife Refuge. In fact, the darkened skies were caused by smoke; given the pure blue skies in every other direction, the smoke was a clear sign of a prescribed burn taking place on refuge land.
The use of fire as a management tool benefits the land in a number of ways. It reduces competition between weedy and native species, allowing native plants to thrive; it returns nutrients to the soil, and improves wildlife habitat.
Many native grasses and wildflowers have such deep root systems they’re unaffected by fast-moving fires, and most animals and birds are able to flee. Burns are planned to minimize the threat to mating or nesting birds, and burn sites often are interspersed with plots that provide refuge for wildlife. Due to the fast-moving nature of such fires, animals such as mice, snakes, and lizards can burrow underground to escape.
For every burn, temperature, humidity levels, wind speed and direction, soil moisture, rain chances, and other factors are taken into account. Even the movement of smoke is important; planning always involves any communities that might be affected. (For a sense of the complexity involved with prescribed burns, this article from the Indiana Division of Fish and Wildlife is instructive. For a sample of a Texas Parks & Wildlife letter sent to burn ‘neighbors,’ click here.)
Because of the complex planning necessary and the possibility of rapidly changing weather conditions, burns sometimes are cancelled at the last minute. When the conditions are right, as they were the weekend of November 13-14, planners rejoice, and the evidence of their planning fills the skies. Because refuge and park lands are so expansive, it can be hard to pinpoint the exact location of a burn, but general areas are easy to spot: Galveston State Park, various refuges, wildlife management areas, and even a few parcels of private land.
A newly-ignited refuge fire seen from Brazoria County Road 208
A later view of the same fire from Hoskins Mound Road, showing different ignition points
The color and density of the smoke adds information for those viewing from a distance. The nature and amount of the fuel make a difference; newly ignited fires tend to billow, while a dying fire produces increasingly thin veils of smoke. The most memorable fire I’ve viewed took place at the Aransas Wildlife Refuge many years ago. In that instance, an absence of wind allowed billows of smoke to build so high that a small pyrocumulus cloud developed.
From time to time during the day, I stopped to watch the fires; by late afternoon, all were nearly extinguished. In the meantime, it was interesting to see them from different perspectives, rising above the same sort of plant communities that would benefit from their presence. 
The next week, while crossing the Seabrook-Kemah bridge on Texas 146, I happened to look to the east, across Galveston Bay. On a far shore, more than twenty miles away, plumes of smoke were rising. Conditions must have been just right; some portion of the Anahuac Wildlife Refuge had been gifted with fire.
Lagniappe 