For Immediate Release: September 1, 2026

Harmful algal blooms (HABs) persist on different areas of Hebgen Reservoir. This could possibly be due to winds pushing algae from one side of the reservoir to the other. No matter the reason, please be aware there continues to be toxic algae present in these areas, and conditions seem to be changing from day to day. NorthWestern Energy is monitoring these blooms and will provide updates if additional restrictions are implemented for public safety.  

Read the full press release here.

While Hebgen Reservoir is monitored regularly, it is very important to remain vigilant with yourself and your pets, when in doubt, stay out! 

The most recent update for ongoing samples is as follows: 

⚠️ Rainbow Point – was a Closure, has been downgraded to Caution. 

⚠️ Corey Springs – was at Closure, has been downgraded to Caution. 

🚫 Yellowstone Holiday (Grayling Arm) – was at Caution, has now been upgraded to Closure.