Published on July 28, 2025 at 3:43 p.m.
Heat, humidity, thunderstorms, this is what marks the summer of 2025 in Quebec so far. But a respite is coming. Forecast.
More than the average
The figures do not lie: summer is hot and humid in southern Quebec in 2025. In particular, in Montreal and Ottawa, there are respectively on average 6.7 and 6.8 days with a feeling of 35 or more. Dated July 27, we resened 14 in Ottawa, and 11 in Montreal. It is more than twice the average for Ottawa, and the month of July is not finished.
Respite in sight
Fortunately, these figures should stop increasing from Wednesday, for a few days. Tuesday is expected to be the last day of heavy heat in the south of the province, at least until next weekend. The temperature will be down, but it is especially humidity that will make the days, and especially the nights, more comfortable.
Sec
In southern Quebec, the maximum will go from 30 ° Tuesday to 24 ° Friday. It is already an appreciable respite. But the disappearance of stifling humidity will be the most decisive factor. We are not talking about a slight decrease, but a considerable decline. For example, the maximum should be 24 ° Friday, and the feeling will be …. 24! The dew point will be between 5 ° and 10 °. So we’re talking about a much drier weather than during last weekend.
Water in the air
The dew point helps quickly assess the amount of water vapor present in the air. This is the temperature at which the air must be cool to reach saturation, so so that humidity becomes liquid. We must first know that the capacity of the air to contain water vapor depends on the temperature. The more hot the air, the more it can contain it. This is why in the early morning, at the time often the coldest of the night, water droplets appear on the lawn and other vegetation. The temperature came down under the dew point, and the humidity in the air was forced to condense on the surfaces. The amount of water vapor in the air is directly linked to the dew point. Relative humidity, expressed as a percentage, is linked to the difference between the dew point and the air temperature. The closer they are, the higher the percentage. When the dew point is greater than 18 °, we start to feel a tropical background. At more than 20 °, the heat becomes heavy to bear. At 22 ° or more, it’s downright overwhelming. The air absorbs steam less well, and our body cannot therefore cool as much thanks to the evaporation of perspiration.
Hot in the west
The descent of a hollow, therefore a mass of cold air, is responsible for this more comfortable episode in southern Quebec. On the other hand, a ridge, therefore hot air, will go up from the United States to the west of the country in the coming days. In Kelowna in particular, mercury should reach 34 ° in the middle of the week. Temperatures will be on the rise in Quebec at the end of the week, but we will still be entitled to at least three days under season, on Thursday, Friday and Saturday.
With the collaboration of Bertin Ossonon, meteorologist.
