This site has now set out four of China's colour-coded weather warnings: typhoons, heat, and rain and fog. Every one of them belongs to the warm half of the year.
The two that own the cold half are missing. Sandstorm appears on this site exactly once, as three words in a month-by-month table cell. 寒潮 (hán cháo, the cold wave) appears nowhere at all. Between them they are the reason a Beijing spring morning turns orange and the reason a Guangzhou December suddenly needs a coat.
They also make the neatest pair in the system, because one of them stops more than any other signal China issues, and the other stops nothing.
The framework, again in one line#
Same instrument, same four rungs, same two-part structure: a published standard that says when the colour is issued, and a 防御指南 (fángyù zhǐnán, defence guideline) that says what ought to happen. The typhoon page sets out the machinery and the rain and fog page sets out the crucial distinction — the guideline is advice to whoever acts, not a switch that closes anything by itself.
The instrument behind all of it is China Meteorological Administration Order No. 16, approved on 11 June 2007, issued on 12 June 2007 and in force from the day of issue. Reading it republished on a provincial government portal confirms the attribution the rain and fog page gives it.
Sandstorm: three colours, and they are measured in metres#
Dust gets no blue. Like heat and like fog, the scale starts at yellow, and it runs on visibility:
| Colour | The standard |
|---|---|
| Yellow | 沙尘暴 possible within 12 hours — visibility under 1,000 m — or already occurring and likely to continue |
| Orange | 强沙尘暴 possible within 6 hours — visibility under 500 m |
| Red | 特强沙尘暴 possible within 6 hours — visibility under 50 m |
Read the Chinese in that table rather than the colours. The phenomenon is renamed at each step: 沙尘暴 (shā chén bào, sandstorm), then 强沙尘暴 (qiáng shā chén bào, strong sandstorm), then 特强沙尘暴 (tè qiáng shā chén bào, extremely strong sandstorm). China is not grading one thing three ways; it is naming three things and attaching a colour to each.
The numbers are worth holding next to the fog scale, which runs 500 m, 200 m, 50 m. Fog and dust converge on the same 50 metres at red, from very different directions.
The red sandstorm guideline is the strictest sentence in the system#
Each colour carries its own defence guideline. Yellow is about windows, hoardings and masks; orange stops open-air and high-level work and puts airports, railways and motorways on protective measures. Red is the one to read exactly:
The other red item is stranger, and it is the opposite of what a red rainstorm does:
学校、幼儿园推迟上学或者放学，直至特强沙尘暴结束
Schools and kindergartens delay the start of school, or delay dismissal, until the extremely strong sandstorm is over. Red rain sends everyone home; red dust keeps them where they are. Air you cannot see through is not something to walk children out into.
Cold wave: four colours, and three things have to be true at once#
The cold wave gets the full scale, and its standard is the most demanding in the system — every level is a three-part test, and all three parts must hold:
| Colour | The fall | Minimum reached | Wind |
|---|---|---|---|
| Blue | 8°C or more in 48 hours | ≤ 4°C | force 5 or above |
| Yellow | 10°C or more in 24 hours | ≤ 4°C | force 6 or above |
| Orange | 12°C or more in 24 hours | ≤ 0°C | force 6 or above |
| Red | 16°C or more in 24 hours | ≤ 0°C | force 6 or above |
Three things move as you climb, and one of them moves only once. The drop steepens at every step. The floor falls from 4°C to freezing at orange and then stops. The wind rises from force 5 to force 6 at yellow and then stops. And blue is the only level with a 48-hour window — every colour above it is a 24-hour forecast.
A cold wave signal is not a statement about cold. It is a statement about a fall. A city sitting at a steady −20°C with no change coming does not qualify for any colour, while a city dropping from 14°C to −2°C overnight in a stiff wind qualifies for orange. This is exactly the trap the rainstorm scale sets with rainfall rate rather than total, and it catches people the same way.
Now read the guideline, and notice that nothing shuts#
Here are the two upper defence guidelines side by side, in full. Orange:
政府及有关部门按照职责做好防寒潮应急工作；注意防寒保暖；农业、水产业、畜牧业等要积极采取防霜冻、冰冻等防寒措施，尽量减少损失；做好防风工作
Red:
政府及相关部门按照职责做好防寒潮的应急和抢险工作；注意防寒保暖；农业、水产业、畜牧业等要积极采取防霜冻、冰冻等防寒措施，尽量减少损失；做好防风工作
That is not an oversight. It is a statement about what a cold snap actually does: it damages crops and animals and it kills vulnerable people indoors, and neither of those is fixed by closing a motorway.
Who the cold wave scale was written for, on the evidence of its own words#
The blue guideline gives it away:
对热带作物、水产品采取一定的防护措施
Take protective measures for tropical crops and aquatic products. The yellow one widens to 热带、亚热带水果 (rèdài, yà rèdài shuǐguǒ), tropical and subtropical fruit, alongside livestock and poultry.
A signal scale whose gentlest rung is worried about tropical crops was not drafted with Harbin in mind. Combine that with the ≤ 4°C and ≤ 0°C floors and the design reads clearly: the cold wave warning is aimed at the parts of China that are not supposed to freeze. It is a southern and central instrument as much as a northern one, which is why a December cold wave is a bigger event in Guangzhou than a colder day in Shenyang.
In practice#
- The colour tells you the visibility, not the discomfort. A yellow sandstorm at 1,000 m is an unpleasant, gritty, photograph-ruining day. Orange at 500 m is a day to change plans. Red is rare.
- Do not treat rail as the sandstorm fallback. It is the one signal whose top colour names trains explicitly, and the compensation position on a Chinese flight delay is no better when the cause is weather.
- Sandstorm season is spring, and it is a northern event. The dust arrives from the Gobi and the northwest, and the month-by-month picture flags the risk for Beijing in March, April and May and nowhere else in the year.
- A mask is in the guideline for a reason. Yellow already tells people to carry 口罩、纱巾 (kǒuzhào, shājīn), masks and scarves, and to keep respiratory patients indoors. Dust is a coarse-particle event, which is a different problem from the fine-particle pollution the air quality index is built around.
- A cold wave will not close anything, so plan around the cold itself. Nothing in the national guideline suspends transport or schooling at any colour. What changes is the temperature, quickly.
- The south is where a cold wave bites hardest, because buildings there are built without central heating. A red cold wave in a place used to 15°C is a harder day than a normal one in the northeast.
- Hong Kong and Macau run their own warning systems under their own rules, with their own names and thresholds, so none of the mainland scale described here applies to a day spent there.
Checked for newer, and what I could not read#
The standards and guidelines above were read on two China Meteorological Administration pages and cross-checked against a provincial government republication of the national Order No. 16, which also supplied the approval and issue dates. The three sources agree word for word on every standard quoted here, and on the cold wave guidelines.
Two things I could not read from here, and say so rather than guess. Beijing published a revision of its own municipal signal catalogue in November 2025, and Jiangsu issued a provincial catalogue in August 2025; both hosts refused requests, so this page does not describe either. That matters because a province or city may set its own thresholds on top of the national scale — so if a local app shows you a colour that does not match the numbers above, the local catalogue is the one that governs, and it is the one to check.
Frequently asked questions#
How many levels does a Chinese sandstorm warning have?#
Three — yellow, orange and red. There is no blue sandstorm signal, the same way there is no blue for fog or heat. Yellow means visibility under 1,000 m within 12 hours, orange under 500 m within 6 hours, and red under 50 m within 6 hours.
What happens during a red sandstorm warning in China?#
Its defence guideline says aircraft suspend takeoffs and landings, trains suspend operation and motorways are temporarily closed, people should stay in a windproof and dustproof place, and schools and kindergartens delay the start of the day or delay dismissal until it is over. It is the only Chinese weather signal whose guideline names trains.
When is sandstorm season in Beijing?#
Spring. March to May is when dust carried from the Gobi and the northwest reaches Beijing and the north China plain, which is why the month-by-month planning guidance flags a dust risk for those months and not for the rest of the year.
What is a cold wave warning in China?#
A four-colour signal — blue, yellow, orange, red — issued on a three-part test: a minimum temperature falling by at least 8, 10, 12 or 16°C, reaching at or below 4°C for the lower two colours and at or below freezing for the upper two, with average land wind force of 5 or 6 and above. Blue looks 48 hours ahead; the others look 24.
Does a cold wave warning close anything in China?#
No. At every colour, including red, the national defence guideline asks for warm clothing, frost and freeze protection for agriculture, aquaculture and livestock, and wind precautions. The orange and red guidelines are identical except that red adds emergency rescue to the government's duties. Nothing is suspended at any level.
Why does China warn about cold waves in the south?#
Because the scale grades a temperature fall rather than a temperature. Its lowest colour requires a drop of 8°C to a minimum of 4°C or below, and its own guideline talks about protecting tropical crops — so a December cold wave is a bigger event in Guangzhou, where buildings have no central heating, than a colder ordinary day in the northeast.