The summer advice on this site is a number. The Yangtze cities are "traditionally called the three furnaces, regularly exceeding 38°C". Turpan "bakes above 40°C in July". August is "peak heat — avoid the east". All true, and all of it treats heat as a climate fact you schedule around, in the way you would schedule around rain.
China does not treat it that way. A hot day there is a declared event, on the same national signalling system this site has already explained for wind.
The framework is one you have already met#
The typhoon guide sets out the four-colour warning scale and the instrument behind it — blue, yellow, orange and red, defined nationally, each carrying a published defence guideline. That page covers the wind thresholds and the rule that the more severe the warning, the less notice it gives you.
Heat runs on the same machinery and is not covered there. It also differs from wind in a way worth knowing before you look at an app.
Heat has three colours, not four#
There is no blue heat warning. The scale starts at yellow, and the three levels are these:
| Colour | The standard |
|---|---|
| Yellow | Three consecutive days with a daily maximum above 35°C |
| Orange | A maximum rising above 37°C within 24 hours |
| Red | A maximum rising above 40°C within 24 hours |
Look at the yellow row again, because it is a different kind of test from the other two. Orange and red are forecasts within a day. Yellow is a statement about persistence — three days running above 35. It is the only one of the three that describes a spell rather than a peak, and it is the one that tells you a week is going to be difficult rather than an afternoon.
That inverts the pattern the typhoon page describes. With wind, severity comes with less notice. With heat, the mildest signal is the one looking furthest ahead.
Red is where outdoor work stops#
Each colour carries its own defence guideline, and they escalate in a way that is legible from the street.
- Yellow — departments prepare heat-prevention measures; the public is advised to reduce outdoor activity in the afternoon; guidance is given for the old, the young and the unwell; people working in the heat take protective measures.
- Orange — heat-prevention measures are implemented; outdoor activity in the hottest hours is avoided; working hours are shortened; vulnerable groups are looked after; and there is an explicit warning about fire risk from heavy electricity use.
- Red — emergency measures; outdoor open-air work stops, special sectors excepted; vulnerable groups protected; particular attention to fire.
So the answer to "why is nobody working on that building site" on a 41-degree afternoon is not stoicism or a local arrangement. It is the red signal doing what its guideline says.
Underneath the signal is a labour rule with numbers#
The stoppage is not only a weather-service instruction. It also sits in an employment instrument, and that one is graded more finely.
The 防暑降温措施管理办法 (fáng shǔ jiàng wēn cuòshī guǎnlǐ bànfǎ, Administrative Measures on Heat Prevention and Cooling), issued in 2012, sets three tiers in its Article 8:
日最高气温达到40℃以上，应当停止当日室外露天作业；日最高气温达到37℃以上、40℃以下时，用人单位全天安排劳动者室外露天作业时间累计不得超过6小时……日最高气温达到35℃以上、37℃以下时，用人单位应当采取换班轮休等方式，缩短劳动者连续作业时间。
Where the daily maximum reaches 40°C or above, outdoor open-air work must stop for the day. Between 37 and 40°C, an employer may schedule no more than six hours of outdoor open-air work across the whole day. Between 35 and 37°C, it must use shift rotation and rest to shorten continuous working time.
Heatstroke is an occupational disease#
One more provision, because it says how seriously the system takes this. Article 19 of the same measures provides that a worker who suffers 中暑 (zhòng shǔ, heatstroke) as a result of high-temperature work or work in hot weather, and is diagnosed as having an occupational disease, receives work-injury insurance benefits.
Heatstroke in China is not merely a medical event. It is a compensable industrial injury with a diagnostic pathway behind it — which is the clearest available statement of what 40°C is understood to be.
What a visitor should take from it#
You are not a worker on a Chinese site, so none of the labour rules protect you. That is exactly why they are useful information: they tell you what the locals have decided the day is worth.
- A red warning is a day to restructure, not push through. If the people paid to be outside have been sent home, a full day of walking a scenic area is a poor plan.
- Orange is the working threshold for a visitor. Above 37, do the outdoor half of the day before eleven and after five, and put something indoors in between.
- Yellow means the spell, not the day. Three days above 35 is a signal to move the outdoor legs of an itinerary, not just an afternoon.
- The indoor half hour is free if you want it. A public library is open, air-conditioned and free by statute, and so is a large museum in most cities.
- Watch the fire warning in the guidelines. Both orange and red flag electrical fire risk from air-conditioning load, which is a reason to take the evacuation plan on your hotel landing more seriously in a heatwave than in February.
- This is a local signal. As with wind, a warning is issued for a place. Check the city you are in and the city you are going to.
Checked for newer, and the answer was mixed#
The national warning instrument — the meteorological administration order the typhoon page names — is still in force, with no repeal or amendment found. That is a result rather than an absence.
Provinces, though, are legislating on top of it. Jiangsu adopted its own provincial measures on the issuance and dissemination of meteorological disaster warning signals on 6 November 2024, in force from 1 January 2025 — and Jiangsu contains Nanjing, one of the furnace cities this site names. Where a province has its own text, it sits above the national baseline rather than replacing it.
On the labour side, several commercial sites circulate a "2025 edition" of the heat-prevention measures. I could not confirm any revision on an official host, so this page describes the instrument as issued and says nothing about a rewrite that may not exist.
Hong Kong and Macau issue their own heat warnings under their own systems, and none of the above describes them.
One more distinction, because the two get confused. Air pollution is not part of this meteorological system at all: it runs on its own three colours, graded on forecast air quality by the environmental authorities, and its response measures are set city by city rather than nationally.
Frequently asked questions#
What do China heat warning colours mean?#
Three levels, not four: yellow for three consecutive days with a maximum above 35°C, orange for a maximum rising above 37°C within 24 hours, and red for a maximum above 40°C within 24 hours. There is no blue heat warning, unlike the wind scale.
Does work stop in China when it is too hot?#
Yes. The published defence guideline for a red heat warning stops outdoor open-air work, special sectors excepted, and the 2012 heat-prevention measures require outdoor open-air work to stop for the day when the daily maximum reaches 40°C. Between 37 and 40°C it is capped at six hours across the day.
Is heatstroke an occupational disease in China?#
Yes. Under Article 19 of the heat-prevention measures, a worker who suffers heatstroke from high-temperature or hot-weather work and is diagnosed with an occupational disease receives work-injury insurance benefits.
How hot does it get in Chinese cities in summer?#
The Yangtze basin cities regularly exceed 38°C in July and August, and the Turpan basin in Xinjiang goes above 40°C. Which months and regions to avoid sets the heat against everything else that makes a month good or bad.
What should I do on a red heat warning day in China?#
Treat it as a day to rearrange rather than endure. Do outdoor sightseeing early and late, keep the middle of the day indoors, and take the warning as evidence rather than atmosphere — outdoor work is required to stop at that level.
Are China heat warnings national or local?#
The scale and its thresholds are national, but each warning is issued for a specific place, so a red signal in one city says nothing about the next. Some provinces, Jiangsu among them, have adopted their own measures on issuing warning signals on top of the national rules.