Your Situation
You need to purify yourself for prayer, but water is genuinely unavailable, or using it would cause you harm (illness, extreme cold, injury).
What to know
Allah has built a specific alternative into the religion for exactly this situation, called tayammum (dry ablution) — it isn't a lesser or informal option, it's a valid, complete substitute for wudu when water genuinely can't be used.
What you can do
- Make your intention (niyyah) to purify yourself for prayer.
- Strike both palms once on clean earth, sand, stone, or a dust-covered surface.
- Blow off any excess dust.
- Wipe your palms over your entire face, once.
- Wipe your right palm over your left hand and arm, and your left palm over your right hand and arm.
- You're now purified and can pray, exactly as if you'd made wudu.
Worth knowing: Tayammum is specifically for when water is absent, hard to reach, or would harm you — not simply for convenience when water is available but inconvenient to get to. If you find water before praying, tayammum is no longer valid and you should use water instead. Some scholars differ on whether one strike suffices for both face and arms, or whether two separate strikes are preferred — the method above (one strike) is well-attested and widely followed.
DeenGuide gives general, sourced guidance — it isn't a fatwa. For your specific personal situation, consult a qualified local scholar.