Six of China's weather warning colours are set out on this site: typhoons, heat, rain and fog, and sandstorms and cold waves. Snow and road ice are not, and the words appear nowhere else here at all.
That is an odd blank for a site with a Harbin page about a city that stages an ice festival at twenty-five below. It is also a missed pair, because these two signals are built on stranger foundations than any of the six.
The framework is the one you have already met — a national scale, a published standard for each colour, a 防御指南 (fángyù zhǐnán, defence guideline) saying what ought to happen, and no automatic closure of anything. The rain and fog page explains why that distinction matters.
Snow: four colours, and the unit is not what you expect#
Here is the thing that surprises people. A Chinese snow warning is not measured in centimetres of snow on the ground. It is measured in millimetres of precipitation — the water the snow melts down to:
| Colour | The standard |
|---|---|
| Blue | 4 mm or more within 12 hours, or already reached and continuing |
| Yellow | 6 mm or more within 12 hours, or already reached and continuing |
| Orange | 10 mm or more within 6 hours, or already reached and continuing |
| Red | 15 mm or more within 6 hours, or already reached and continuing |
Fifteen millimetres sounds like nothing until you remember what it is measuring. Snow is mostly air, so a given depth of water on the ground arrives as a much greater depth of snow — the ratio varies with how wet the snow falls and is not fixed by the standard. What the standard does fix is that red means fifteen millimetres of water inside six hours, which is a great deal of snow in a working day's worth of hours.
The architecture is the same one the rainstorm scale uses: the lower two colours share a twelve-hour window and differ in quantity, then the window halves and the quantity climbs again.
What the snow guidelines ask for#
Blue and yellow are about preparation and are nearly identical — transport, rail, power and telecoms departments patrol and clear the lines, pedestrians watch their footing, drivers fit anti-skid measures, herding areas stock up on feed, and temporary structures get reinforced against the weight of snow.
Orange drops the farming detail and adds 减少不必要的户外活动, reduce unnecessary outdoor activity, and an instruction to bring livestock into shelter.
Red is where transport appears:
必要时停课、停业（除特殊行业外）；必要时飞机暂停起降，火车暂停运行，高速公路暂时封闭
Where necessary, classes and business stop, special industries excepted. Where necessary, aircraft suspend takeoffs and landings, trains suspend operation, motorways are temporarily closed.
Road ice: the only signal that does not measure the weather#
The second winter signal is the genuinely unusual one. It has three colours — no blue, like fog and heat — and its standard is a compound condition rather than a quantity:
| Colour | The standard |
|---|---|
| Yellow | Road-surface temperature below 0°C, precipitation occurring, and road icing affecting traffic possible within 12 hours |
| Orange | The same two conditions, with significant icing possible within 6 hours |
| Red | The same two conditions, with severe icing possible or already present within 2 hours |
Every level begins 当路表温度低于0℃，出现降水 — when the road-surface temperature is below zero and precipitation is falling.
That is 路表温度 (lùbiǎo wēndù), the temperature of the road surface, not of the air. It is the only signal in this system that grades a thing on the ground rather than the sky. The standard would have no reason to specify the road surface if it always matched the air, and it is that gap — a road below zero under an air temperature above it — that the signal exists to catch.
Note the red window too. Two hours — tying the shortest notice any Chinese weather signal gives, which is the red fog signal.
What the road-ice guidelines escalate#
The instruction to drivers sharpens in a way worth reading as a three-step ladder:
- Yellow — 驾驶人员应当注意路况，安全行驶: drivers should watch road conditions and drive safely.
- Orange — 驾驶人员必须采取防滑措施，听从指挥，慢速行驶: drivers must take anti-skid measures, follow directions and drive slowly.
- Red — 交通、公安等部门注意指挥和疏导行驶车辆，必要时关闭结冰道路交通, and 人员尽量减少外出: traffic and public security departments direct and divert vehicles and where necessary close the iced road, while people minimise going out.
A pedestrian instruction runs alongside the driving one at every level: yellow tells people to cycle less and mind their footing, orange repeats the anti-slip warning, and red asks them to stay in. Two audiences, one signal, and the walking half is easy to skim past.
In practice#
- The colour is a forecast about the road, not a verdict on your day. For road ice especially, orange is the level at which a hired car becomes a bad idea and the reasons not to drive yourself in China get a seasonal one added.
- Rail is the winter fallback, with a caveat. Trains appear in the red snow guideline only where necessary, which is a much weaker instruction than the one dust carries — so a red snow signal is not by itself a reason to assume your train is cancelled.
- Two hours is not a plan. A red road-ice signal can arrive two hours out. If a winter morning departure matters, the margin has to exist the night before.
- Harbin is a special case and not a warning-heavy one. A city built around a deep cold winter treats snow as ordinary; what a Harbin winter actually asks of a visitor is about clothing and daylight far more than about signals.
- Millimetres, not centimetres. If a Chinese forecast quotes you a snow figure, check which it is before deciding whether to move a flight.
- Hong Kong and Macau do not issue these signals at all, having no use for them, and run their own systems for the hazards they do face.
Frequently asked questions#
How is a Chinese snow warning measured?#
In millimetres of precipitation — the water content of the snow — rather than in the depth of snow on the ground. Blue is 4 mm within 12 hours, yellow 6 mm within 12 hours, orange 10 mm within 6 hours and red 15 mm within 6 hours. As a rough conversion, a millimetre of water becomes about a centimetre of snow, though that varies with how wet it falls.
Does a red snow warning close airports and railways in China?#
Not automatically. Its defence guideline says that where necessary aircraft suspend takeoffs and landings, trains suspend operation and motorways close. That conditional wording is absent from the red sandstorm guideline, which states the same three suspensions flatly — so a red snow signal means closures are being considered rather than executed.
What is China's road ice warning?#
A three-colour signal — yellow, orange, red — issued when the road-surface temperature is below 0°C and precipitation is falling, with icing affecting traffic expected within 12, 6 or 2 hours respectively. It is the only Chinese weather signal that grades a surface rather than the atmosphere, which is why a road can ice up on a day the air temperature is above freezing.
How much notice does a red road ice warning give?#
Two hours, which ties the red fog signal for the shortest lead time in the Chinese warning system. The upper road-ice colours also carry the strongest driving instruction: at orange, drivers must take anti-skid measures and drive slowly.
Should I take the train instead of flying in a Chinese winter?#
The guidelines give one reason to lean that way: the red snow signal treats suspension of trains, flights and motorways alike as conditional, and roads carry a second signal of their own for icing, which neither runways nor railways do. That is a statement about how the system watches each mode, not a promise about any given day.
Do snow warnings affect visiting the Harbin ice festival?#
Rarely in the way visitors expect. Harbin's winter is designed around cold rather than disrupted by it, and the practical concerns are clothing, short daylight and transfers rather than warning colours. The signals matter more for travel days into and out of the northeast than for the festival itself.