Grassy Lake, WY

As of 2026-09-30, Grassy Lake sits at 7179.10 ft, which is low for this time of year. Over the past 30 days the level has fallen 2.09 ft.

The most recent reading at Grassy Lake is 7179.10 ft (2026-09-30), sourced from the U.S. Bureau of Reclamation. Readings on this page refresh automatically as the agency publishes new data.

The highest level for Grassy Lake in our records is 7210.83 ft on 2022-06-07. The lowest is 7178.38 ft on 2026-09-17. Our record covers about 4 years of readings.

Compared with every September in our records, the current level is higher than 8% of them, which we classify as low for this time of year. Seasonal comparison matters more than the raw number, because most reservoirs draw down predictably through late summer and refill over winter and spring.

Reservoir levels move for four main reasons: rainfall and runoff into the basin, releases through the dam for downstream water supply, power generation or flood control, evaporation during hot months, and seasonal drawdown schedules set by the operating agency. Grassy Lake has fallen 2.09 ft over the past 30 days. For the operational reason on any given week, check the U.S. Bureau of Reclamation directly.

Grassy Lake is -11.53 ft compared with this date last year (7179.10 ft today). The full-history chart above covers 4 years, with a record high of 7210.83 ft and a record low of 7178.38 ft.