At least six dams along the Front Range have already collapsed and water has overflowed more than a dozen others, according to officials from the Division of Water Resources. Several more dams in Larimer County, near the Wyoming border, are in danger of collapsing. Many spillways have been activated, aggravating downstream floods. Some municipal water-treatment plants have scaled back operations because of rising floodwaters.

The storm that caused the heavy rains was the result of a seasonal monsoon flow north from the Gulf of Mexico that collided with a cold front moving down from Canada. The weather system has been stalled over the Front Range since Monday, creating what local forecasters are calling “100-year-or-worse floods.” Scattered showers with some pockets of heavier rain are expected through the weekend.