At a glance
いつまで～のやら means "who knows how long ~ will go on". The speaker, often talking to themselves, uses it to show worry or exasperation about something that keeps going.
いつまで + [plain form] + のやら
この雨はいつまで降るのやら。 Who knows how long this rain will go on.
How to form it
のやら attaches to the plain form. Nouns and な-adjectives take な before のやら.
| Attaches to | Form | Example |
|---|---|---|
| Verb | plain form + のやら | いつまで続くのやら |
| Verb (ongoing) | ている + のやら | いつまで寝ているのやら |
| い-adj | plain form + のやら | いつまで寒いのやら |
| Noun / な-adj | + な + のやら | いつまで学生なのやら |
| Register | Colloquial, a little old-fashioned, monologue-like | Not polite, not formal |
The の can be dropped after verbs: いつまで降るやら is also correct.