Sunday on the Black Sea coast will be cloudy but dry, with highs of 16C to 18C, the National Institute of Meteorology and Hydrology (NIMH) said.
The sea is 19C, with waves of 2-3 on the sea-state scale.
Overnight and today, cloud across Bulgaria will vary and often be thick, with almost no rain. In the morning, visibility will be poor in some valleys in western Bulgaria. Lows will be 2C to 7C and highs 13C to 18C. A light to moderate wind will blow from the west-northwest. Air pressure will rise and go above the average for the month.
The mountains will also be cloudy and almost dry, with a moderate to strong northwest wind. Highs will be about 8C at 1,200 metres and about 2C at 2,000 metres.
On Monday, most of the country will see thick cloud. In western Bulgaria it will clear in places and be mostly sunny. Fog will form before noon in some lowlands and valleys.
Light showers are possible in the mountains and in a few places in the northeast. The wind will be light to moderate, from the northwest. Morning temperatures will be 3C to 8C, and afternoon highs 15C to 20C.
Tuesday will be mostly sunny, with more cloud over eastern Bulgaria. The wind will shift to the south-southeast and temperatures will rise.