A major temperature drop is coming to Mattawa, Ontario, in 2026, with overnight lows forecast near −22°C by mid‑week. The surge of Arctic air should accelerate ice formation on local water bodies, including the Mattawa and Ottawa Rivers and sheltered basins such as Otto Lake — but the rate of ice growth will depend on surface snow and whether water is moving beneath the ice.
Even though the air will get much colder mid‑week, a thick blanket of snow acts like an insulating “down comforter,” slowing how quickly the ice underneath can harden. The North Bay‑Mattawa Conservation Authority (NBMCA) monitors snowpack, water levels and related watershed conditions. Scientists and regional ice‑safety guidance note that snow cover can reduce ice growth rates by roughly 50% or more, which can produce slushy pockets where the weight of snow presses thin ice below the waterline and allows water to pool and hide weak spots.
Local outfitters, including Mattawa River Resort, advise people to check ice thickness before skating or fishing — for example, by drilling test holes with an ice auger and measuring in multiple locations. Moving water complicates the picture — particularly on the Ottawa River — because regulated flows and dam operations can change levels and flows rapidly. The Ottawa River Regulation Planning Board warns that flow rates and actual levels can change quickly and that regulation affects river conditions; these changes can create hazards beneath the surface that are difficult to detect from above.
The Ontario Provincial Police (OPP) — North Bay/Mattawa — reiterate standard ice‑safety guidance: “No ice is ever 100% safe.” Residents should not go out alone, should tell someone where they are going, and should check ice thickness in several places (using a reliable tool such as an auger) to ensure it can support their weight.
Bottom line: the mid‑week cold will help ice form, but recent snow and freezing rain have created patchy, deceptive conditions. Test the ice yourself in multiple spots, follow local authority guidance, and treat all ice with caution.
