If you do a search on taking your snakes outside, you will find a few good threads on the topic

I wouldn't keep the snake in direct sunlight for too long if you plan on going outside with your animal. The sun can get pretty hot and remember, these guys are nocturnal so they don't ever naturally lay out in the hot sun.

As long as the temperatures aren't too high or too low you should be fine for 30 minutes or so.

If you have a temp gun, that would be a great way to make sure your snake isn't getting too hot or too cold.