A change in the weather is coming that will open its doors in autumn.

BarcelonaThe bout of heat and muggy conditions we've experienced in recent days, which have felt more like late August than late September, will give way to a change in the weather that will begin to manifest itself this Sunday, but will become even more evident at the beginning of next week. The approach of a front and a cold air jam will reactivate instability with showers and thunderstorms that will affect all parts of the country throughout the day. This has led Meteocat to issue a warning for heavy rain in all regions (yellow in general, but with some regions in the far south and northeast at orange), and the Civil Protection Agency has activated the Inuncat plan alert.

Temperatures will begin to drop on Sunday, with lows often falling late in the day, but highs that will remain virtually unchanged along the coast and will drop more significantly in the Pyrenees and Pre-Pyrenees. Next week, we'll notice the full force of the cooling down throughout the area due to the arrival of cold air from the polar regions. Temperatures will even be below average, with generally quite cool temperatures and possibly the first dusting of the season in the high Pyrenees. Autumn will officially arrive on Monday night, and it will make a grand entrance.

Sunday: significant change in weather

The approach of the cold air pocket will cause a significant increase in instability. During the night and early morning, there will already be thunderstorms in the Pyrenees and the Lleida Pre-Pyrenees, as well as some weak, scattered showers in some coastal and pre-coastal areas, often barely wetting the ground.

Showers and thunderstorms will gain ground throughout the afternoon and evening and could appear in any region, with some significant downpours accompanied by hail. The highlight of the episode will be the thunderstorms that will form from mid-afternoon between Terres de l'Ebre and northern Castellón, as well as the rain that will affect the eastern Pyrenees and nearby regions, where it will rain heavily for several hours. In these areas, rainfall could easily exceed 30 l/m2 or 40 l/m2 throughout the day.

A complicated day, keeping an eye on the sky, especially after midday. Mountain activities are not recommended, especially without appropriate clothing, as the relatively mild morning weather will quickly be replaced by cool, or even chilly, evenings. Furthermore, this is the weekend return day, so be careful on the roads if you're caught driving in the rain. Early in the morning, we won't notice the change in temperature, but throughout the day the mercury will drop, especially inland and in the Pyrenees, where the coolness will already be evident. Many lows will be recorded at the end of the day.

Monday: Soda is everywhere

The week will already begin with a much cooler atmosphere, as temperatures will drop everywhere, with lows close to 5°C in the Pyrenean valleys and between 10°C and 14°C in much of the interior of the country. We will therefore be talking about a very cool and fully autumnal atmosphere on the day we enter astronomical autumn. We will still be doing so with traces of clouds, although clearings will gain ground during the morning. Showers will recur in the northeast in the afternoon, generally more scattered and weaker.

Fresh strength next week

Cold air from the polar regions will hit us hard next week. We're looking forward to much cooler days, more reminiscent of October than mid- to late-September. Starting Tuesday, highs will barely exceed 22 or 23°C, with chilly nights in many inland regions and mountainous areas, where temperatures will drop below 0°C for the first time in many months. Autumn will begin with a firm start on Monday at 8:19 p.m.