Sydney and parts of New South Wales experienced unseasonably warm weather over the weekend, with temperatures more than 10°C above the typical September average. This early heat is part of a typical "spring rollercoaster," where weather patterns can shift rapidly between warm and cool conditions. A wave of heat swept across south-eastern Australia, reaching its peak in Sydney on Monday before a sudden drop in temperature occurred. In Sydney’s outer west, temperatures climbed to 35.4°C in Richmond and 35°C in Penrith, just before a cold front, known as a "south-southeasterly change," moved in. At Sydney’s Observatory Hill, temperatures peaked at 32.7°C before plummeting by about 10°C within a couple of hours, according to the Bureau of Meteorology. On the weekend, easterly sea breezes helped keep coastal areas a few degrees cooler than the western suburbs. Western Sydney recorded temperatures of about 34°C on Sunday, while the city center was slightly cooler at 28.9°C. The Bureau of Meteorology described the warmth as "unseasonably warm," with temperatures 6°C to 12°C above the September average. For example, Sydney’s Observatory Hill usually has a September maximum of 20.1°C, but it reached 32.7°C, while Penrith typically sees 23.5°C, but hit 35°C. The hot, dry, and windy conditions led authorities to issue high to extreme fire danger warnings for Monday, particularly in the Greater Hunter region and parts of the north-eastern and northern inland areas. Now, Sydney residents can expect a cooler and wetter outlook for the coming days due to a cool southerly airstream. Temperatures in the city are expected to drop to the high teens, between 18°C and 19°C, on Tuesday, before warming slightly to 22°C to 24°C on Wednesday. The temperatures will gradually rise through the rest of the week, but another cooler change is forecast to arrive next weekend. Regional areas such as Cessnock, Muswellbrook, and Singleton are expected to reach 35°C, with extreme fire risk, according to Weatherzone. However, the Bureau of Meteorology said that fire danger will decrease across much of the state starting Tuesday, following the arrival of the cool change. A strong El Niño is developing in the Pacific Ocean and is expected to peak in late spring or summer, potentially reaching levels warmer than any observed since 1950. Climate experts believe this El Niño, combined with climate change, could push global temperatures to record highs in 2027. This winter was the third-warmest on record in Australia, with New South Wales, Tasmania, and Victoria experiencing their hottest winter ever. El Niño typically brings warmer and drier conditions to Australia, increasing fire risk in summer, especially in regions that have had little rain. Authorities have urged NSW residents to check the state’s rural fire service (RFS) website for the latest updates on fire risks and warnings.