Learn Hardcore Japanese: asita ha tabun ame desu. - It will probably be rainy tomorrow.

In this sentence, は is the topic particle. Historically, the topic particle is written は but pronounced “wa.” So 明日は is read “ashita wa.” It marks “tomorrow” as the topic: “As for tomorrow, …”

What exactly does は do here?

は marks the topic or sets up contrast. 明日は roughly means “as for tomorrow.” It frames what follows as information about tomorrow. Without は, 明日 simply acts as a time expression; with は, you’re thematically anchoring the sentence to tomorrow and can also imply contrast (e.g., today is not rain, but tomorrow probably is).

Can I drop は and just say 明日たぶん雨です?

Yes. 明日たぶん雨です is natural in casual conversation. Using は makes the topical/contrastive nuance explicit, while dropping it sounds a bit snappier and is very common in speech. Both are fine here.

Can I use に after 明日, like 明日に?

Not in this structure. 明日にたぶん雨です is unnatural. With a noun + です predicate about weather, use 明日(は). The time particle に is typically used with verbs (e.g., 明日には雨が降ります, adding emphasis/contrast). For plain scheduling, you’d normally say 明日行きます rather than “明日に行きます.”

Where does たぶん go? Can I move it?

Yes. Common placements include:

明日はたぶん雨です。
たぶん、明日は雨です。
明日は雨でしょう。たぶん。 (the last one is very conversational) Adverbs like たぶん usually appear before the clause or near the predicate they modify. Don’t put たぶん after です.

Why is there no verb like “to rain”? Why just 雨です?

Japanese allows nominal sentences with the copula です. 雨 is a noun (“rain”), so 雨です is “(the weather is) rain.” It’s a natural way to talk about weather categories, especially in forecasts. If you want an explicit verb, you can use 雨が降る (“rain falls”). For example: 明日はたぶん雨が降ります。

Which sounds more natural: 雨です, 雨が降ります, or 雨でしょう?

明日はたぶん雨です。 Conversational and understandable; sounds like a personal assessment.
明日は雨が降ります。 Neutral statement with a verb; good for describing the event of raining.
明日は雨でしょう。 Very common for forecasts or polite conjecture. You can combine with たぶん: 明日はたぶん雨でしょう。 This is arguably the most “forecast-like.”

Should I use でしょう, と思います, or かもしれません with たぶん?

All are possible, with slightly different feels:

明日はたぶん雨でしょう。 Polite conjecture; sounds measured and forecast-like.
明日はたぶん雨だと思います。 “I think” softens it as your personal opinion.
明日は雨かもしれません。 “It might rain” (weaker than たぶん); you can add もしかしたら for emphasis: もしかしたら明日は雨かもしれません。

How strong is たぶん compared with other words like おそらく, きっと, もしかしたら?

Rough guide to perceived certainty (highest → lowest):

きっと (“surely”) > おそらく (“very likely”) > たぶん (“probably”) > もしかしたら／もしかすると (“maybe/perhaps”). Use context and tone to fine-tune; these aren’t strict percentages.

Why is there no explicit subject like “it”?

Japanese often omits subjects, especially in impersonal statements. Weather is commonly expressed without an overt subject. 雨です literally “(is) rain” is fully grammatical and natural. If you really want a subject, you can use a verb construction: 雨が降ります (“rain falls”), where 雨 is the grammatical subject.

Can I use が after 明日, like 明日がたぶん雨です?

Not in this simple sentence. 明日が雨です is usually odd unless you’re answering a very specific contrastive question like “Which day is rainy?” Even then, a clearer option is 雨が降るのは明日です (“The day when it rains is tomorrow”).

What’s the casual version of this sentence?

明日はたぶん雨だ。 (plain copula)
Very casual and common: 明日はたぶん雨。 (copula dropped) You can add particles for tone: 明日はたぶん雨だね。 (“probably rain, huh”) or 明日はたぶん雨だよ。 (“it’s probably rain, you know”).

How can present です refer to the future?

Japanese doesn’t have a dedicated future tense. The non-past form (like です／だ／降る) can refer to present or future. The time word 明日 (“tomorrow”) supplies the future meaning: “(It is) rain (tomorrow).”

How do I pronounce 雨, and how do I avoid confusing it with “candy” (飴)?

Both are read “ame,” but in Tokyo pitch accent:

雨 (rain): HL (á-me) — first mora high, then drop.
飴 (candy): LH (a-mé) — rises to the second mora. Kanji and context remove ambiguity in writing; in speech, pitch and context help.

Are there different readings for 明日?

Yes:

あした (ashita): Most common in everyday speech.
あす (asu): Formal/announcement/broadcast style; common in weather reports.
みょうにち (myōnichi): Very formal/literary. All pair fine with this pattern: 明日はたぶん雨です, あすはたぶん雨です, etc.

Do Japanese normally put spaces between words like in 明日はたぶん雨です?

No. Spaces are added for learners. A natural written sentence is: 明日はたぶん雨です。 (with a Japanese period 。)

Can I say “tomorrow’s weather” explicitly, like 明日の天気は…?

Yes. For forecasts: 明日の天気は雨でしょう。 This explicitly frames it as “tomorrow’s weather.” Saying 明日はたぶん雨です is shorter and sounds more conversational.

How would I say “It’s raining (now)” versus this “probably (future)” sentence?

“It’s raining (now)”: 雨が降っています。
“It will probably rain tomorrow”: 明日はたぶん雨でしょう。 or 明日はたぶん雨が降ると思います。 Use the progressive 〜ています for ongoing actions.