This year's 'San Fu' period, the hottest time of summer in traditional Chinese calendar, is set to begin on July 15 and will last for 40 days, which is 10 days longer than last year's duration.

According to Yang Jing, a member of the Chinese Astronomical Society and director of the Tianjin Astronomical Society, the start of the 'San Fu' period is determined by the 'Geng' days in the traditional Chinese sexagenary cycle. The period begins on the third 'Geng' day after the Summer Solstice, marking the start of the initial 'Fu'. The fourth 'Geng' day signals the middle 'Fu', and the first 'Geng' day after the Beginning of Autumn marks the final 'Fu'.

The initial and final 'Fu' periods are always fixed at 10 days each. However, the length of the middle 'Fu' can vary, being either 10 or 20 days. This variation depends on the number of 'Geng' days occurring between the Summer Solstice and the Beginning of Autumn. If there are four 'Geng' days, the middle 'Fu' lasts 10 days; if there are five, it extends to 20 days.

Consequently, the total 'San Fu' period can be either 30 days, known as a 'short San Fu', or 40 days, referred to as a 'long San Fu'. Taking 2026 as an example, calculations show the initial 'Fu' from July 15 to 24, a 20-day middle 'Fu' from July 25 to August 13, and the final 'Fu' from August 14 to 23.

Statistically, the 40-day 'long San Fu' is more common. Data from 2001 to 2050 indicates that 34 years will experience the long version, compared to only 16 years with the short version. Yang Jing explains that the approximately 47-day interval between the Summer Solstice and the Beginning of Autumn frequently accommodates five 'Geng' days.

Regardless of its length, the 'San Fu' period represents the year's peak of heat and humidity. Yang Jing advises the public to focus on heatstroke prevention, dietary adjustments, and daily routine management to cope with the challenging weather.

Weather Forecast for Changsha

Following the start of 'San Fu', Changsha is forecasted to experience predominantly sunny and hot weather in the coming week, with maximum temperatures reaching 37°C to 39°C. From mid-July to August, conditions are expected to be hotter and drier than average, with a high risk of meteorological drought.

The influence of Typhoon 'Bavi', now weakened to a tropical storm and located in Anhui province, has ended for Changsha. Over the next week, the city will see mainly sunny and hot weather. Scattered showers or thunderstorms are possible from the 16th to the 17th, followed by a period of moderate rain with localized heavy rain from the 18th to the 19th.

The forecast from mid-July to August predicts rainfall 20% to 40% below the seasonal average and a significant increase in the number of high-temperature days, with 20 to 25 days exceeding 35°C. There is a high risk of moderate or higher-level meteorological drought developing from early August onward. Additionally, 2 to 3 landfalling typhoons are expected to potentially impact the Changsha area.

Detailed Forecast for Changsha

July 13-15 (Monday to Wednesday): Sunny to partly cloudy. South wind force 3. Highs 37-39°C, Lows 28-30°C.

July 16-17 (Thursday to Friday): Sunny to partly cloudy, with afternoon to evening showers or thunderstorms. South wind force 2-3. Highs 36-38°C, Lows 28-30°C.

July 18 (Saturday): Cloudy turning to moderate thunderstorms, with localized heavy rain. South wind shifting to north wind force 2. High 33°C, Low 26°C.

July 19 (Sunday): Light rain turning to cloudy. North wind force 2. High 32°C, Low 26°C.

Mid-July to August Climate Outlook

The central and eastern equatorial Pacific is currently in an El Niño state, which is expected to develop into a moderate or stronger event during summer and autumn. For the peak summer period from mid-July to August, the Changsha area is projected to experience significantly less rainfall, more high-temperature days, and potential typhoon impacts.

Rainfall is expected to be 20% to 40% below the seasonal average, totaling 140-180 mm. The number of days with temperatures above 35°C is forecast to be 20-25, which is 10-15 days more than usual, with extreme highs potentially reaching 39-40°C. Meteorological drought is likely to develop rapidly from early August, with a high risk of moderate or severe drought.

Typhoon activity in the Northwest Pacific and South China Sea is expected to be frequent from late July to mid-August, with 2 to 3 landfalling typhoons potentially affecting the region.

Key Precautions for the 'San Fu' Period

The public is advised to stay vigilant during this extended period of intense heat and humidity. Essential precautions include staying hydrated, avoiding prolonged outdoor exposure during peak heat hours, using air conditioning or fans to maintain a cool indoor environment, wearing light and breathable clothing, and adjusting diets to include lighter, hydrating foods. Special attention should be given to the elderly, children, and those with pre-existing health conditions.