Updated · 4 min read · Mango Tour editorial, Sanya
In short: Sanya has two seasons. November to April is dry — 3 to 7 rainy days a month, 27–32 °C by day, sea 23–27 °C. May to October is hot and humid — 31–34 °C by day, sea around 29 °C, 10 to 17 rainy days a month, and typhoons are possible from June to October. The month-by-month figures are below, with what they mean for a trip.
Sanya weather by month
Day and night air temperature, sea temperature off the south coast, monthly rainfall and the number of rainy days.
- January — 27 / 20 °C, sea 24 °C, 6 mm, 3 rainy days
- February — 28 / 21 °C, sea 23 °C, 14 mm, 4 days
- March — 30 / 23 °C, sea 24.5 °C, 21 mm, 4 days
- April — 32 / 25 °C, sea 26.5 °C, 51 mm, 6 days
- May — 34 / 27 °C, sea 28.5 °C, 131 mm, 10 days
- June — 34 / 27.5 °C, sea 29.5 °C, 182 mm, 14 days
- July — 33 / 27 °C, sea 29 °C, 212 mm, 14 days
- August — 33 / 27 °C, sea 29 °C, 227 mm, 16 days
- September — 33 / 26 °C, sea 29.5 °C, 249 mm, 17 days
- October — 31 / 25 °C, sea 28.5 °C, 236 mm, 13–14 days
- November — 30 / 23 °C, sea 27 °C, 74 mm, 7 days
- December — 28 / 21 °C, sea 25 °C, 16 mm, 4 days
Where the figures come from
Air temperatures are 2016–2025 averages for the Sanya station of the China Meteorological Administration (CMA); they run half a degree to a degree above the 1991–2020 climate normals. Rainfall and rainy days are CMA climate normals. Sea temperatures are ten-year satellite averages; in a cool winter the sea can drop to 21–22 °C. These are long-term averages, not a forecast for your dates.
All figures are for Sanya and the south coast. Haikou, in the north of the island, is noticeably cooler and cloudier in winter.
The dry season: November to April
Rainfall ranges from 6 mm in January to 74 mm in November, with 3 to 7 rainy days a month, and humidity of 74–83 % — mild for the tropics. December to February brings 27–28 °C by day and 20–21 °C in the evening, so a light layer is useful. In January and February the sea is fresh, around 23 °C, and a north-easterly wind can raise waves in open bays; Yalong Bay and Xiaodonghai, sheltered by headlands, are calmer.
March and April warm up: 30–32 °C by day, and by the end of April the sea is around 26–27 °C.
The wet season: May to October
The hottest days come in May and June, around 34 °C, with nights of 27 °C. Rainy days rise to 10–17 a month and humidity to 79–85 %. August, September and October are the wettest months, with 227–249 mm each, while the sea stays at 28.5–29.5 °C. Rain often comes as afternoon downpours, but overcast spells happen too; schedule excursions for the morning. October is almost as wet as September — the dry season really starts in November.
Typhoons: when, and how much of a risk
Long-term records show typhoons making landfall on Hainan mostly between June and October, most often in September. According to the Hainan Climate Centre, in September and October an average of about three tropical cyclones affect the island and fewer than one makes landfall. They tend to come ashore in the north and north-east, but flights and sea programmes in the south are cancelled too: in October 2016 Typhoon Sarika led Sanya airport to cancel more than 200 flights.
For itineraries in summer and autumn this means: no boat trip on the last day, a buffer for connections, and travel insurance.
Strong sun all year
The average UV index in Sanya ranges from 8 in December to 12 from March to September — very high to extreme even in winter. Sunscreen, a hat and sunglasses are needed in every month.
Which months to choose
- Dry and warm without the heat — November to April.
- Warm sea in the dry season — December and April.
- Lower prices and fewer people — May, June and the second half of October.
- Holidays matter more than weather: Chinese New Year (6 February 2027) and National Day week (1–7 October) are the price peaks.
