Vietnamese weather expressions do not require a dummy pronoun corresponding to English it, and property predicates do not require an obligatory equivalent of be. Trời lạnh means “It is cold,” with trời as an environmental noun and lạnh as the predicate. In a context where the weather is obvious, speakers can simply say Lạnh quá! “So cold!”
Weather grammar therefore combines ordinary Vietnamese resources: direct property predicates, event predicates such as mưa, existential có for environmental phenomena, and locative or temporal frames. This page focuses on those patterns. General causative and light-verb uses of làm are left to Light Verb Làm.
Trời is meaningful, not a dummy it
Trời literally refers to the sky, heavens, or ambient weather environment. In weather clauses it often supplies an environmental subject:
Trời lạnh, nhớ mang áo khoác nhé.
It's cold, so remember to bring a jacket.
Hôm nay trời đẹp, mình đi bộ ra hồ đi.
The weather is lovely today; let's walk to the lake.
Trời tối rồi, chúng ta về thôi.
It's dark already; let's go home.
English it in these translations refers to nothing. Vietnamese trời is not an empty substitute for that pronoun; it names the ambient environment against which lạnh, đẹp, or tối is predicated. This is why it can also retain its ordinary lexical meaning in expressions about the sky.
When the setting is understood, Vietnamese freely omits trời:
Nóng quá! Mở cửa sổ được không?
It's so hot! Can we open the window?
Tối rồi, đừng đi một mình.
It's dark now; don't go alone.
These are not missing-subject errors. Vietnamese allows a contextually recoverable environmental subject or topic to remain unspoken. In a forecast, contrast, or careful statement, trời is more likely to be expressed.
Weather events: mưa, nắng, and changing conditions
Some weather words behave as event or state predicates. Mưa means “rain/be raining”; it does not need a separate verb equivalent to English rain. Nắng describes sunny conditions and can occur with trời or in a contextually subjectless clause.
Trời đang mưa, đợi một lát rồi hãy đi.
It's raining; wait a while before leaving.
Sáng nay mưa rất to, nhưng chiều lại nắng.
It rained heavily this morning, but it turned sunny again in the afternoon.
Có vẻ sắp mưa; mây đen kéo đến rồi.
It looks as though it is about to rain; dark clouds have moved in.
Đang presents the rain as ongoing, sắp as imminent, and rồi as a new situation or achieved transition. The predicate mưa itself never conjugates. In the past-time frame sáng nay, bare mưa readily receives a past reading.
The word nắng is common in trời nắng “it is sunny” and in contrasts such as mưa ... nắng. For an event of the sun shining, Vietnamese may use a fuller expression such as nắng lên. Register and regional habits influence fine choices, but the everyday patterns here are neutral nationwide standard Vietnamese.
Environmental properties predicate directly
Temperature, light, quietness, humidity, crowding, and cleanliness can be expressed with property predicates. The relevant setting may be the subject or a fronted frame.
| Setting | Predicate | Example |
|---|---|---|
| trời ambient weather | lạnh, nóng, đẹp | Trời lạnh. |
| phòng này room | tối, sáng, nóng | Phòng này tối. |
| ngoài đường outside/street frame | đông, ồn | Ngoài đường đông lắm. |
| ở đây local frame | yên tĩnh, mát | Ở đây khá yên tĩnh. |
Trong phòng hơi tối, nhưng ngoài hành lang rất sáng.
The room is a little dark, but the corridor is very bright.
Ngoài đường đông lắm vì mọi người đang đi làm.
The streets are very crowded because everyone is going to work.
Degree words normally precede the property: rất lạnh “very cold,” hơi tối “a little dark,” khá yên tĩnh “quite quiet.” Sentence-final quá often conveys an exclamatory “too/so”: Nóng quá! Inserting là before these properties is an English-transfer error.
Existential weather and environmental phenomena
Use có when presenting a phenomenon as present: wind, fog, frost, a storm, or smoke. A locative or temporal phrase can establish its domain.
Sáng nay có sương mù dày đặc trên đường cao tốc.
There was dense fog on the motorway this morning.
Ngoài biển đang có bão, nên tàu chưa được rời cảng.
There is a storm at sea, so the boats have not yet been allowed to leave port.
Hôm nay có gió, ngồi ngoài sân sẽ mát hơn.
It is windy today; sitting in the courtyard will be cooler.
The difference between direct property predication and existential presentation is meaningful. Trời nhiều mây describes the sky as cloudy; Trên trời có nhiều mây presents many clouds in the sky. Trời gió is not the general template for “It is windy”; trời có gió or simply có gió is natural because the wind is presented as present.
Negation follows the predicate type. Trời không lạnh negates the property “cold.” Hôm nay không có gió denies the presence of wind. Ngoài đường không đông denies the property “crowded.” Do not force all three into không có simply because English may use there isn't or it isn't.
Formal forecasts and measurements
Everyday speech favors short environmental clauses. Weather forecasts and technical reporting use fuller noun phrases and measurements (formal):
Nhiệt độ cao nhất hôm nay là ba mươi hai độ C.
Today's highest temperature is 32 degrees Celsius. (formal)
Khu vực ven biển có mưa vừa, có nơi mưa to.
Coastal areas will have moderate rain, with heavy rain in some places. (formal forecast style)
In the measurement clause, là identifies the value of the highest temperature; it does not precede an adjective. Forecasts often omit an overt future marker because the forecast context supplies prospective time. They also use compact phrases such as có nơi “in some places,” a conventional formal forecast pattern.
Casual conversation may instead say Hôm nay chắc mưa “It'll probably rain today” or Ngoài trời lạnh lắm “It's very cold outside.” Both registers use invariant predicates; their difference lies in vocabulary, information density, and context.
Time, viewpoint, and environmental change
Compare bare, progressive, imminent, and change-of-state framings:
| Frame | Example | Interpretation |
|---|---|---|
| bare property | Trời lạnh. | cold conditions hold |
| ongoing event | Trời đang mưa. | rain is in progress |
| imminent event | Trời sắp mưa. | rain is about to begin |
| new state | Trời lạnh rồi. | it has become/is now cold |
| return/contrast | Trời lại mưa. | it is raining again / contrary to expectation |
Particles and context supply aspectual structure around an unchanged predicate. That structure is why “Vietnamese has no conjugation” does not mean that all weather clauses have the same temporal interpretation.
A natural exchange
A: Ngoài trời thế nào? B: Đang mưa và hơi lạnh. Tôi thấy phía tây có mây đen, chắc trời còn mưa lâu. A: Vậy mình ở đây làm việc nhé; đừng ra quán cà phê nữa. B: Được. Ở đây có trà nóng không? A: Không có, nhưng tôi sẽ làm cà phê. Cửa sổ bị hở nên trong phòng cũng lạnh; lát nữa anh Minh đến, nhờ anh ấy xem giúp.
A: What's it like outside? B: It's raining and a little cold. I can see dark clouds to the west, so it will probably keep raining for a while. A: Then let's stay here and work; don't go to the café. B: All right. Is there hot tea here? A: No, but I'll make coffee. The window doesn't seal properly, so it is cold inside too; Minh will arrive later, and we'll ask him to take a look.
The reply uses an understood environmental subject with đang mưa and hơi lạnh. Có mây đen presents clouds, ở đây expresses staying/location, and có trà nóng không asks about availability. Thấy, làm, đi, đến, được, and bị retain their own meanings and unchanged forms.
Quick decision aid
- Is the claim a property of the weather or setting? Predicate it directly: Trời lạnh, phòng tối.
- Is it a weather event? Use the event predicate: (Trời) mưa, optionally with đang, sắp, rồi, or lại.
- Is a phenomenon being presented as present? Use có: có gió, có sương mù.
- Is the environment obvious in casual speech? The subject may be omitted: Nóng quá!
- Are you giving a measurement or identity value? Là may link the measured noun to its value: Nhiệt độ là ...
- Never insert a Vietnamese pronoun merely to imitate English dummy it.
Common Mistakes
1. Inventing a dummy pronoun for English it.
❌ Nó lạnh hôm nay.
Incorrect if nó is intended as meaningless weather ‘it’; nó normally refers to an identifiable entity.
✅ Hôm nay trời lạnh.
It is cold today.
Use trời as a meaningful environmental subject or omit it when context allows.
2. Inserting là before a property predicate.
❌ Trời là lạnh và phòng là tối.
Incorrect English-style use of là before properties.
✅ Trời lạnh và phòng tối.
It is cold, and the room is dark.
Lạnh and tối predicate directly.
3. Using có for every weather description.
❌ Trời có lạnh hôm nay.
Incorrect as a neutral statement meaning ‘It is cold today’; có would require a special emphatic or question-related context.
✅ Hôm nay trời lạnh.
It is cold today.
Use existential có for a phenomenon such as gió or sương mù, not automatically before a property.
4. Adding a past ending to a weather predicate.
❌ Sáng nay mưa-đã rất to.
Incorrect: Vietnamese does not attach a past-tense ending to mưa.
✅ Sáng nay mưa rất to.
It rained very heavily this morning.
The time phrase supplies the past reading. Separate đã is possible only when its realized/prior viewpoint contributes to the discourse.
Key Takeaways
Vietnamese weather clauses use meaningful environmental subjects such as trời, contextually omitted subjects, direct property predicates, event predicates, and existential có. There is no dummy weather it and no obligatory be before lạnh, nóng, tối, or similar properties. The predicates do not conjugate; time phrases and particles such as đang, sắp, rồi, and lại create precise temporal and aspectual readings.
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- Absence with Không CóA2 — Negate possession and existence with không có, control the scope of negation, and distinguish absence from negative location.
- Light Verb LàmA2 — How làm builds actions, occupations, results, and causative predicates without conjugation.
- Là for Classification and IdentificationA2 — Use là to identify a person or thing, assign it to a noun-defined class, and distinguish this pattern from property, location, possession, and existence clauses.
- Lại: Return, Repeat, and CounterdirectionA2 — Distinguish lại as return toward a reference point, repetition after a predicate, retention, and responsive counteraction.