On Tuesday, September 17, the weather in Bulgaria will be marked by considerable cloudiness, with rain showers spreading gradually from the northwest towards the southeast. In the northeast and in mountainous regions, rainfall will be more intense, and thunderstorms are also expected. During the afternoon hours, skies will begin to clear quickly from the northwest. A moderate to occasionally strong northwesterly wind will draw in cooler air, bringing down daytime temperatures. Maximum values will range from 21°C to 26°C, reaching 27–28°C in the far southeast and in parts of the Upper Thracian Plain, while in Sofia highs will remain around 21°C.

Along the Black Sea coast, the morning will begin with sunshine and passing clouds. By midday, however, cloud cover will thicken, starting from the northern coast, where rain is forecast. Later in the evening, showers will extend to the southern coast. Winds will shift during the day, from light to moderate from the south-southwest in the morning to temporarily strong from the northwest in the afternoon. Daytime temperatures will reach 24–26°C, while the sea temperature will hold steady at 23–24°C.

In the mountain regions, skies will remain largely overcast, with rain in some areas and a likelihood of thunderstorms, especially over the Rhodopes. By afternoon, clearer intervals will spread from the northwest. Winds will be moderate to strong from the northwest throughout the day. At 1,200 metres, temperatures will hover around 16°C, while at 2,000 metres they will drop to about 9°C.