The Oldman River is running hard through Lethbridge tonight.
The river is under a high streamflow advisory and is expected to peak Wednesday evening between 750 and 1,000 cubic metres per second. As of Tuesday morning the flow was approximately 615 m³/s. The Oldman typically runs at 200 to 250 m³/s this time of year. Tonight's peak will be more than three times the seasonal average and the highest the city has seen in several years.
The City of Lethbridge has been direct about what that means: higher than usual, but well below the threshold for overland flooding. The river valley parks and coulee trails are where the concern is tonight.
Stay off the river valley trails
The city is monitoring river valley parks and trails and will proactively close impacted low-lying areas as levels rise. Crews are already in place. The north lane on westbound Whoop-Up Drive is closing daily to allow vehicles to access the river valley.
Everyone is asked to stay off river valley trails entirely until levels return to normal. This applies whether or not a specific area has been formally closed. Riverbanks are unstable. The rain has made the soil along the coulees significantly less stable than it looks.
"The biggest thing that people need to be aware of is the instability of the riverbanks — it is probably one of the biggest dangers that's out there," said Charles Schoening, Water Rescue team lead with Lethbridge Fire and Emergency Services. "That's both the flow in the river and the water, the rain making the soil less stable around the riverbanks. Make sure to avoid those areas, stay on solid ground, roadways, pathways, and keep dogs and children well away from those areas as well."
Local storm ponds are also significantly higher than normal, with some surrounding pathways submerged. Stay a safe distance from all storm ponds and obey posted closure signs.
A boat advisory is in effect on the Oldman River. The river exceeds recommended safe flow rates for boating or swimming. Do not enter the water.
Report downed trees in public spaces to Lethbridge 311.
Why the river peaks tonight, not when the rain stopped
The rain over Lethbridge has eased. The river will peak tonight anyway.
The Oldman is fed by tributaries draining from the Rockies and foothills west of Lethbridge. Rain that fell further up the watershed takes time to travel down through the river system before it reaches the city. The crest arrives in Lethbridge well after local rainfall stops.
"Because it's feeding in from all the tributaries and the rain may take a little longer to taper off in the mountains as well, the high water, the crest will happen well after the rain is done in Lethbridge," said Schoening.
After tonight's peak, levels are expected to gradually drop. The situation should improve through the rest of the week.
The water treatment plant and what it means for your tap
The Oldman River is Lethbridge's drinking water source. High flows increase turbidity the amount of sediment suspended in the water — which forces the treatment plant to slow down production to maintain safe treatment standards.
The plant has reduced output from 60 million litres per day down to 50 million litres per day. The city is drawing on local reservoirs to make up the difference. Rainfall over the past 24 hours pushed flow through the system dramatically higher than normal.
"On an average day, we see about 40 million litres per day and last night we reached over 100 million litres per day of flow. That's the additional flow just from the rainfall," said Jason Drenth, General Manager of Wastewater, Water and Electric Utilities for the City of Lethbridge.
Tap water is safe to drink. The city is asking residents to reduce non-essential water use until the river stabilizes and the plant returns to full capacity. Run dishwashers and washing machines only when full. Skip lawn watering for now.
This is not 1995 or 2013
The 1995 flood is still a reference point for anyone who lived through it. The "flood of the century" on the Oldman caused severe damage to the river valley, knocked out bridges, and changed how Lethbridge thought about the river for years afterward. And 2013 brought the worst flooding across southern Alberta since 1897 — deaths, billions in damage, and communities evacuated from Canmore to Calgary.
Tonight is neither of those. The 750 to 1,000 m³/s peak is the highest the city has seen in several years and it warrants taking the river valley seriously. It does not warrant alarm about the broader city. The advisory is a high streamflow advisory. There is no flood watch. There is no flood warning. Overland flooding is not forecast.
Stay out of the river valley tonight. The rest of Lethbridge is fine.
Where to check for updates
City of Lethbridge road and facility closures: lethbridge.ca/news/road-and-facility-closures
Alberta River Forecast Centre advisories for the Oldman River system: albertariverforecast.ca
Environment Canada real-time flow data for the Oldman River near Lethbridge, station 05AD007: wateroffice.ec.gc.ca
To report downed trees or hazards: Lethbridge 311
Sources:
City of Lethbridge, spokesperson statements and updates, June 3, 2026
Charles Schoening, Water Rescue team lead, Lethbridge Fire and Emergency Services, June 3, 2026
Jason Drenth, General Manager of Wastewater, Water and Electric Utilities, City of Lethbridge, June 3, 2026
Alberta River Forecast Centre, High streamflow advisory, Oldman River, June 2026 (albertariverforecast.ca)
City of Lethbridge, Road and Facility Closures page (lethbridge.ca)
