ame no hi ni kuruma o untensuru toki wa ki o tsukete kudasai.

Please be careful when driving a car on rainy days.

Breakdown of ame no hi ni kuruma o untensuru toki wa ki o tsukete kudasai.

• は: topic particle
• 車くるま: car
• を: direct object particle
• の: possessive case particle

Questions & Answers about ame no hi ni kuruma o untensuru toki wa ki o tsukete kudasai.

Why is の used in 雨の日? Is 雨日 a thing?

• の links two nouns, letting the first modify the second: 雨の⽇ = “day of rain” → “a rainy day.”
• 雨日 exists but is rare/archaic and not used in everyday modern Japanese.
• Other common ways to say “rainy weather”: 雨の日, or the more formal 雨天（うてん）.

What does に after 日 do in 雨の日に? Can I drop it?

• に marks time: 雨の⽇に = “on a rainy day.”
• You can sometimes omit に with time words: 日曜日(に)行く. Here, keeping に makes the timing inside the clause clear: 雨の日に車を運転する (“to drive a car on a rainy day”).
• Another natural option is to topicalize: 雨の日は、車を運転するとき… (As for rainy days, when you drive…).

Why is it 車を運転する and not 車で運転する?

• 運転する is a transitive verb: you “drive a car,” so the car is the direct object with を: 車を運転する.
• で marks means/vehicle for movement verbs: 車で行く (go by car).
• 車で運転する is redundant/unidiomatic; avoid it.

What’s the difference between ときは and ときに here?

• ときは topicalizes the whole “when…” clause and presents a general rule/advice. That matches this sentence’s tone.
• ときに marks the specific time something happens. It can work, but it sounds more like focusing on a particular occasion.
• For broad advice, prefer ときは.