To build on the good answers from superkret and nemo…

The survival Rule of 3’s says that, depending on your situation, you can generally survive:

• three weeks without food.
• three days without drinkable water.
• three hours in a harsh environment (extreme heat or cold).
• three minutes without breathable air, or in icy water.

Finding a way to stay warm and dry at night should probably be your primary concern. Hypothermia kills fast.