Wednesday morning will be cloudy on the Black Sea coast, with fog in places. The sun will break through before noon and temperatures will reach 17-19C, the National Institute of Meteorology and Hydrology (NIMH) forecasts. The sea is 17-18C, with waves of about 2 on the scale.
Forecasters said on Tuesday that Friday will bring rain and cooler weather. NIMH has now added details for Thursday.
Background: Weather: up to 26C tomorrow, rain and cooler weather arrive on Friday
Tuesday night into Wednesday will be clear and almost windless in most areas, with lows of 5-10C, and about 6C in Sofia. Eastern Bulgaria will have thick cloud and fog in places. Elsewhere on the plains and along the rivers, visibility will be poor but will improve by noon. Air pressure is higher than the monthly average and is barely changing.
Inland, Wednesday will be mostly sunny and warmer, at 21-26C, and about 21C in Sofia. Broken medium and high cloud will pass over in the afternoon. The mountains will also be sunny, with about 16C at 1,200 metres and about 8C at 2,000 metres.
The wind will blow from the south-southwest and will mostly be moderate, but for a time it will be strong in eastern Bulgaria and north of the mountains. On the coast, the wind will be moderate, from the south-southeast.
Rain is expected in a few places in western Bulgaria on Wednesday night into Thursday. On Thursday morning the cloud will briefly break up, then thicken again from the west, and by evening it will rain in places in western Bulgaria. The wind will come from the south-southeast, and it will stay fairly warm: above 20C in most of Bulgaria, with lows mostly between 8C and 13C.
A cold front will approach Bulgaria on Thursday night into Friday. Northwestern Bulgaria can expect heavy rain and thunderstorms.
On Friday the front will cross the whole country. It will be mostly cloudy, with rain in many places, and some parts of central and eastern Bulgaria will get heavy rainfall. The wind will turn northwest and pick up, bringing cool air, and daytime temperatures will be 5-6 degrees lower.
The sky will begin to clear from the west towards Friday evening.