How did the warm fall impact the natural world? Durango, Colorado Fri 69% chance of precipitation Weather affects river levels, animal behavior, bird migrations, plant life Tuesday, Dec. 22, 2020 5:18 AM Updated: Tuesday, Dec. 22, 2020 2:33 PM Dave Sugnet fly-fishes in the Animas River on Dec. 9 in Durango, when daytime temperatures reached the low 50s. The lack of precipitation in Southwest Colorado this fall has left rivers near all-time lows. Jerry McBride/Durango Herald With warm temperatures during the day and cold temperatures at night, the bottom of a river – rather than the top – can start to freeze, which can impact fish eggs incubating in the gravelly river bottom.