When you think about hiking, we always ask ourselves a few questions:

• How far are we hiking? How long will it take?
• What is the weather like?
• How much water do we need to bring?

All of this determines how much water we need, and what we need to bring with us for each hike. Let’s use my Havasupai backpacking trip as an example:

Since temperature isn’t too hot, we can follow the rule of thumb: 0.5 liter per 1-hour of hiking; the average time to hike 1-mile is 30 minutes. To simplify this:

Based on average numbers & rule of thumb:
0.5 liter per 2 miles.

With this equation, I was able to easily calculate that for my Havasupai trip, I will need 3-liter of water for my 12-mile hike. Although it is “obvious” that if you know there will be sun and rain, and you know you should bring sunblock and a light rain jacket – not a lot of people do this. I can’t stress enough, bring it. It is for your own good.

I personally prefer a packable rain jacket because it saves space whether it is for a day hike or backpacking. If you bring one, try to store it in a easily accessible place for sudden down pours. You may even want to have it strapped to the outside of your bag, because staying dry for your hike is crucial – especially if you still have a long way to go. Read about us hiking in the rain at Haleakalā for 8 miles »