If an outdoor drain (like a downspout or yard drain) is frozen:

Frozen Out: How to Unfreeze a Drain Pipe Safely When winter temperatures drop below -6°C (20°F), your plumbing is at high risk. A frozen drain pipe can be more than just an inconvenience; if left unaddressed, the expanding ice can cause pipes to burst, leading to costly water damage.

, which can cause pipes to crack or burst. Start your efforts at the point closest to the drain opening and work backward toward the frozen blockage to allow melted water to escape. Balkan Sewer And Water Main Proven DIY Methods Hair Dryer or Heat Gun

If standing water is in the sink or tub, a shop vac is your best friend.