Pick a day or time to accomplish this. Make sure you're not rushed and you can truly take the time to appreciate what you're about to do.
Pick a form/kata/routine. Choose something you're familiar with and can practically do in your sleep. The last thing you'll want to do is stop to think about the basics. This is a time to explore beyond just learning the steps and movements.
Pick a location. Find somewhere where you have lots of space. If you're uncomfortable about having an audience, pick somewhere isolated.
Absorb and learn from your surroundings
The ground beneath you
Consider the location where you picked. What is the surface like? Chances are if you've been practicing inside the whole time, the outdoor surface will be very different. Even a simple grassy field can pose different challenges. The earth is not smooth. It has ridges and rocks, dips and folds.
If dry, it's crunchy under foot. If green, it's probably at a different temperature from the air around it. The grass hides the earth beneath. It could be soft and muddy or hard and rocky. You won't know until you step down. Depending on the length and type of grass, it could tickle against your feet, trying to distract you as you move. Can you compensate for these things? Can you keep going?
Much of the coastal area around me are rocky. Rocks pose a different challenge from grass. You can see the mounds of rocks and their unevenness. But visual cue is not always enough and the path is not always linear. Maneuvering on rocks requires you consider your next move and plan how you choose to step. You must adjust your step and balance to the surroundings and compensate for the gaps and rises.
Sand is one of my favorite surfaces to walk on. Regardless of if the sand is wet or dry, your feet naturally sink into the surface and you need an extra effort to make the next move. When working in sand, you have to be careful you don't twist too quickly or move without first breaking the grip the sand has on you feet.
I love working in and around water because there's natural energy that fills the air around any body of water. With that being said, working on the water poses its own challenges. Not only is every slippery and you need to be conscious of where and how you step, water has its own flow and movement. Working in water is a great test of balance in the presence of forces pushing against you. But for all the struggles, water is also great to work in if you pains or struggle to move in certain manners under full gravity.
The air around you
Beyond the surface, being outside means dealing with the environment. Is it cold? Is it hot? Is it sunny? Is it windy? Each of these different environmental changes can impact how you perform even the most basic of forms. Understanding your personal limits in these environments and how you compensate for these distractions is a powerful lesson in understanding yourself.
The sounds and smells
When we're training, we primarily use our sense of sight and touch. Being outside provides us with a unique opportunity to develop our other senses. As the air drifts in and out, we are introduced to new sounds and smells that we wouldn't have found on our training floor. Allow oneself to become aware of all this helps to build a total body training.
Enjoy your training
So as we enjoy the nice weather, don't forget to take the opportunity and train outdoors. Become closer to nature and the roots of your Martial Arts and gain a better understand of yourself and your style.