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Dictionary (at least Jisho and WWWJDIC) defines them as:

  * 気象{きしょう} = weather, climate
  * 天気{てんき} = weather, the elements
  * 天候{てんこう} = weather

They all have quite similar definitions, so I don't quite understand the
difference. I would appreciate if someone could shed some light into this (in
English preferably), i.e. when to use each of these words.

Then there is the word 気候{きこう}, which I think means climate, and cannot be
used to describe the weather on a specific day. Is that correct?

Thank you in advance!
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2014-12-16T17:12:53.093
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2014-12-18T15:27:16.020
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question
word-choice words nuances synonyms
What is the difference between all the weather words: 気象{きしょう}, 天気{てんき} and 天候{てんこう}?
天気 (1-3 days): You'll hear 天気 used the most, as in 天気予報 _weather forecast_ or
天気はいいですか _Is the weather good today?_ You should almost always translate 天気 as
"weather" in English.

天候 (2-10 days): 天候 refers to the overall state of the atmosphere between a few
days to about 10 days. Its use isn't that common, however, in casual
conversation it shows up in the phrases 悪天候 "bad weather", referring the the
weather in the past week or two, or 天候に恵まれる "we've been blessed by the
weather."

気候 (climate) can be translated into English as weather or climate, depending
on the context, however, it's used to refer to timescales on the order of a
year. For example, カイロの気候はいいですか is the weather/climate in Cairo good? In this
case, you mean climate, but in English it's rare to ask "How's the climate
where your from?". Rather, "How's the weather where your from?" already
implies you mean weather on a large scale, season to season.

気象 (meteorological phenomena): For example, 気象学者=meteorologist but
天気予報官=weatherman. 気象 refers to weather/climate, as well, but in a bit more
quantitative context regarding changes in pressure and temperature, not simply
"hot" or "cold". An English equivalent would be, "I'm studying meteorology"
vs. "I'm studying weather." Studying meteorology means you're studying
weather, but if you merely said, "I'm studying the weather" it doesn't
necessarily carry with it the quantitative scientific connotation associated
with the word meteorology.
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2014-12-16T17:28:42.143
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answer
### 天気

This is the most common word for _weather_ , and expresses a naive concept of
**the entire perceptive state of sky (and air) in some place at some moment**.
It includes sunshine, cloudage, precipitation, wind, humidity and temperature,
but not likely air pressure. By _at some moment_ I mean, this word is expected
to state an overall impression at a certain time-point, or in a short
timespan, which has no complex changes of state needed to mention.

You can assume a unit of 天気 to be a piece of information that a single column
of a table in the newspaper's forecasting section can describe.

* * *

**On actual usage of the word 「天気」**

```

    ○ 良い天気          天気が良いです。
    ○ 晴れの天気        天気は晴れです。
    ？ 晴れている天気    天気(は/が)晴れています。
    × 寒い天気          天気(は/が)寒いです。
    ○ 死ぬほど寒い天気  天気(は/が)死ぬほど寒いです。
    △ 涼しい天気        天気(は/が)涼しいです。
    
```

If you'd like to use the word 天気 itself in a sentence, you should take care
that most expressions people like to use with 天気 are subjective evaluations
(row #1) or metaphors. Only this sort of expressions can used with 天気 without
limitation.

When you need a word that means a part of 天気 (be sunny, rainy, windy etc.) to
explain 天気, don't use it adjectively (#3) but appositively (#2). 天気 usually
rejects such "a round circle" type attributions. Though, in many cases, it's
enough to mention them without 天気: `晴れています` "It's sunny."

Don't say `暑い天気` and `寒い天気`, because the two words already contain "feel
hot/cold in environment" senses (#4). You can however put your comments to
make them subjective statements: `寒すぎる` or `死ぬほど寒い` (#5).

Other objective words also generally don't get along with 天気, for example,
`涼しい天気` is only valid when it means " _comfortably_ cool".

* * *

### 天候

It also refers to **the state of atmosphere observed in a place** , but this
one **mainly describes successive shift or tendency in a period of time**. In
a short term whose time lapse can be ignored, it becomes interchangeable with
天気.

Since this word is an unnativized Sino-Japanese compound carries formal mood,
we don't use it much in casual conversation. If I say "the weather turns bad"
with `天気`, I prefer `天気が悪くなる`, but with `天候`, `天候が悪化する`. I expect from
`この一週間の天気` the weathers of Sunday, Monday, Tuesday..., but from `この一週間の天候` a
description of how weather changes, getting warmer or colder, whether typhoons
come or not, and so on.

Other usage is basically the same as that of `天気`.

### 気象

This could be translated as _meteorological phenomenon_ or _"meteorologies"_ ,
but not very common to be used as noun (as in `異常気象` "abnormal meteorology").
The main usage of it is as adjective, _meteorological_ (as in `気象衛星`
"meteorological satellite"). This word refers to each **physical phenomenon
detached or not observable from a single viewpoint**.

As you can see, satellites only monitor `気象` and not `天気` or `天候` (unless you
say that the solar wind or the magnetosphere oscillation is `地球の天気`). You
can't mention El Niño and La Niña as `天気` or `天候`, either.

### 気候

Basically identical to _climate_ , that is **a unique environmental feature of
a location** never changes overnight.

You want to live in Florida because `気候が良い`, to go for a trip to Florida not
Louisiana because `天候が良い`, and to choose to go to FL not LA tomorrow because
`天気が良い`.
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answer