Grimsby, Ont. is in for a warm and humid week as a late-summer air mass settles over the region, bringing daytime highs in the mid-20s and off-and-on showers through mid-week. The Weather Network says a “sticky September air mass” is in place across southern Ontario, with a “ring of fire” pattern ushering in muggy air and daily chances for rain and thunderstorms.
As of Monday afternoon, conditions at Vineland Station showed a temperature of 19.5°C with partly cloudy skies, 49 percent humidity, and light winds. No weather alerts are currently in effect for Grimsby or the St. Catharines-Grimsby-Northern Niagara Region, according to Environment Canada.
Daytime highs are expected to climb to 26°C on Tuesday and Thursday, with humidex values reaching 27 to 29, making it feel more like summer than mid-September. The forecast calls for a mix of sun and cloud on Tuesday with a 40 percent chance of showers late in the afternoon. Showers are also likely Tuesday night and Thursday morning, with the greatest precipitation amounts possible on Thursday.
Environment Canada notes that localized flooding is possible in southern Ontario because of the moisture-laden air mass, especially if caught by a thunderstorm. Forecasters warn that a stalled frontal boundary will meander north and south over the next few days, creating high uncertainty in exact temperature and precipitation forecasts.
This humid pattern is part of a broader fall outlook driven by an exceptionally strong El Niño event. Meteorologists with The Weather Network say the pattern favours more mild spells than cold snaps across Canada, delaying the arrival of persistent winter conditions. For Grimsby, that means the warm, sticky weather may linger well into the autumn.
