Far North Ontario weather for August 25, 2026: Sandy Lake faces showers and thunderstorms while KI, Sachigo Lake, Ogoki Post and Fort Severn stay warmer before a sharp midweek cool-down.

Thunder Bay – Weather Desk – Ontario’s Far North is seeing two very different weather stories this Tuesday. Sandy Lake is cloudy and unsettled with a 70 percent chance of showers and a thunderstorm risk, while KI/Big Trout Lake and Sachigo Lake start quieter with temperatures expected to reach the low 20s. Farther east, Marten Falls/Ogoki Post and Wasaho Cree Nation/Fort Severn remain unusually warm for late August, with highs of 25°C and 27°C respectively.

The broader change arrives Wednesday and Thursday. Cooler north and northwest winds spread across the region, with Fort Severn dropping from 27°C today to only 16°C Wednesday and 13°C Thursday. KI, Sachigo Lake and Ogoki will also cool sharply by Thursday.

Today’s Weather Overview

KI / Big Trout Lake — Kitchenuhmaykoosib Inninuwug

Current Conditions

At 5:00 AM CDT, Big Trout Lake Airport was reporting partly cloudy skies and 14.3°C. Humidity was 87 percent, barometric pressure was 101.3 kPa, and winds were light from the west-southwest at 5 km/h. Visibility was 16 kilometres.

The morning begins mainly sunny before cloud cover increases. Environment Canada forecasts a high of 23°C, with a humidex of 27 and a moderate UV index of 5.

Tonight will be cloudy with a 30 percent chance of showers late this evening and overnight. The low falls to 14°C.

Sachigo Lake

Current Conditions

Sachigo Lake is using observations from Big Trout Lake Airport. At 5:00 AM CDT, conditions were partly cloudy at 14.3°C, with humidity at 87 percent, pressure at 101.3 kPa, and west-southwest winds at 5 km/h.

Clouds increase this morning, leaving a mainly cloudy Tuesday. The high reaches 23°C, with a humidex of 27 and a moderate UV index of 4.

Tonight remains cloudy before becoming partly cloudy near midnight. The overnight low is 14°C.

Sandy Lake

Current Conditions

Sandy Lake has the wettest forecast of the communities in this report. At 5:00 AM CDT, Sandy Lake Airport was reporting cloudy skies and 14.7°C. Humidity was 93 percent, pressure was 101.0 kPa, and south-southeast winds were blowing at 8 km/h.

Tuesday stays cloudy with a 70 percent chance of showers and a risk of a thunderstorm. The high reaches 20°C, with a moderate UV index of 4.

Tonight remains cloudy with a 60 percent chance of showers. A thunderstorm remains possible early this evening before the risk diminishes. The low is 13°C.

Anyone travelling by boat or spending an extended period on the land should keep an eye on changing skies today, particularly where thunderstorms develop.

Marten Falls / Ogoki Post

Current Conditions

At 6:00 AM EDT, Ogoki Post Airport was reporting clear skies and 12.1°C. Humidity was 81 percent, barometric pressure was 101.4 kPa, and winds were from the south-southwest at 8 km/h. Visibility was 16 kilometres.

Fog patches dissipate this morning, followed by a mix of sun and cloud. South winds increase to 20 km/h this afternoon, while temperatures climb to 25°C, with a humidex of 27. The UV index reaches 6, or high.

Clouds increase tonight, bringing a 40 percent chance of showers late this evening and overnight along with a risk of a thunderstorm. Southwest winds develop at 20 km/h, with a low of 14°C.

Wasaho Cree Nation / Fort Severn

Current Conditions

At 6:00 AM EDT, Fort Severn Airport was reporting mostly cloudy skies and 14.4°C. Humidity was 90 percent, pressure was 101.0 kPa, and west winds were blowing at 11 km/h. Visibility was 16 kilometres.

Clouds will clear early this afternoon, allowing Fort Severn to warm dramatically to 27°C. The humidex reaches 30, with a moderate UV index of 5.

Tonight brings increasing cloudiness and a 40 percent chance of showers overnight. North winds develop at 20 km/h late this evening, signalling the arrival of much cooler air. The low will be 12°C.

Tomorrow’s Forecast

Wednesday, August 26

KI / Big Trout Lake: A mix of sun and cloud with a 30 percent chance of showers. Northwest winds become 20 km/h gusting to 40 late in the morning. High 21°C. Wednesday night turns cloudy with a 30 percent shower chance and a low of 8°C.

Sachigo Lake: A mix of sun and cloud with a 30 percent chance of afternoon showers. Northwest winds reach 20 km/h gusting to 40. High 21°C, followed by a cloudy night with a 30 percent chance of showers and a low of 8°C.

Sandy Lake: A mix of sun and cloud with a 30 percent chance of afternoon showers. Northwest winds become 20 km/h gusting to 40 late in the morning. High 21°C. The overnight low is 9°C.

Marten Falls/Ogoki Post: Cloudy with a 70 percent chance of showers. Northwest winds increase to 20 km/h gusting to 40 late in the morning. The high reaches 20°C. Wednesday night retains a 40 percent shower chance with a low of 9°C.

Wasaho Cree Nation/Fort Severn: The sharpest change arrives here. Mainly cloudy skies come with a 40 percent chance of showers, while north winds increase to 30 km/h gusting to 50. The daytime high reaches only 16°C, followed by a low of 6°C Wednesday night.

Thursday, August 27 — Much Cooler Across the Far North

Thursday brings a widespread late-summer cool-down.

KI / Big Trout Lake and Sachigo Lake both see a mix of sun and cloud with a 30 percent chance of showers and highs of only 15°C. Overnight lows fall to 6°C.

Sandy Lake is a little milder at 18°C, with a mix of sun and cloud and a 30 percent chance of showers. Thursday night falls to 8°C.

Marten Falls/Ogoki Post reaches only 16°C, with a 30 percent chance of showers. The overnight low is 6°C.

Fort Severn will be the cold spot with a high of just 13°C and a 30 percent shower chance. Thursday night settles near 7°C.

Friday, August 28

Conditions begin to stabilize Friday.

KI and Sachigo Lake will see a mix of sun and cloud with highs near 18°C, while Sandy Lake warms to 21°C. Ogoki Post reaches 19°C with a 30 percent chance of showers.

Fort Severn remains much cooler, with a mix of sun and cloud and a high of only 13°C.

Wardrobe Recommendations

Tuesday still supports lighter late-summer clothing in Fort Severn and Ogoki Post, where highs reach 27°C and 25°C. Sunscreen and sunglasses are useful at Ogoki, where the UV index reaches the high category.

For Sandy Lake, a water-resistant jacket and sturdy footwear are the better choice because showers are likely and thunderstorms are possible. KI and Sachigo Lake can start the day lighter, but keeping a rain shell nearby for tonight and Wednesday is sensible.

The bigger wardrobe change comes Wednesday night and Thursday. Highs fall into the mid-teens in KI, Sachigo Lake, Ogoki and Fort Severn, while overnight lows reach 6°C to 9°C. A hoodie, fleece or light insulated jacket will become much more useful, especially for people travelling early in the morning, working outside or spending time on the water.

Weather Trivia

Fort Severn illustrates just how dramatic late-summer temperature swings can be near Hudson Bay. Environment Canada lists a normal August 25 high of about 16°C for Fort Severn, yet Tuesday’s forecast calls for 27°C. By Thursday, the forecast high drops to 13°C.

Ogoki Post is also running unusually warm today. Its normal daytime high is about 18°C, compared with Tuesday’s forecast of 25°C.

The warmth will not last. The shift toward north and northwest winds Wednesday will help pull much cooler air southward across the Far North, producing the sharp temperature drop expected by Thursday.

Source: Environment and Climate Change Canada observations and forecasts issued early Tuesday, August 25, 2026. KI, Sachigo Lake, Ogoki and Fort Severn forecasts were issued at 5:30 AM EDT; Sandy Lake’s forecast was issued at 4:30 AM CDT.