On cold days, a heater is necessary.

Your cooperation is needed for this project.

I need you.

It's very cold today, isn't it?

On cold days, warm coffee is the best.

On a cold winter night, hot cocoa is the best.

The cold has become severe.

It's difficult to go outside in this coldness.

On a cold winter night, a kerosene heater is indispensable.

A day has 24 hours.