London weather forecast: One last warm day before cooler, wetter conditions arrive Londoners will experience one final day of summer-like warmth on Tuesday, with temperatures reaching 26 C. However, a cooler air mass is set to move in on Wednesday, bringing cloudy skies and a significantly lower high of 16 C. The unsettled weather pattern is expected to persist throughout the week, with a high likelihood of showers and windy conditions later in the forecast period. Londoners can expect one more taste of summer-like weather Tuesday before a cooler and wetter pattern settles into the region for the rest of the week. Environment Canada is calling for a mix of sun and cloud Tuesday, with temperatures climbing to a high of 26 C and a humidex value of 33. There's a 40 per cent chance of showers early in the day and a 30 per cent chance of showers late in the afternoon, along with the risk of a thunderstorm. The chance of showers and thunderstorms will linger into the evening before skies become partly cloudy overnight.Cooler air mass arrives WednesdayThe temperature is forecast to fall to 13 C. A cooler air mass will arrive Wednesday, bringing mainly cloudy skies and a 30 per cent chance of morning showers. The daytime high is expected to reach 16 C before dipping to 7 C overnight. The unsettled weather pattern is expected to continue through the remainder of the week.Thursday's forecast calls for cloudy conditions and a 30 per cent chance of showers, with a high of 14 C. Shower chances increase to 70 per cent Thursday night. Friday is expected to remain cloudy with a 70 per cent chance of showers and windy conditions. The temperature is forecast to top out at 14 C before dropping to about 4 C overnight. By Saturday, temperatures will cool further, with cloudy skies and a forecast high of just 9 C.