The following is my advice to clients on how to avoid the pitfalls of an outdoor speaking engagement:
Wind: Stay on the lee side of the wind—keeping your back to it—so that the microphone isn’t noisily swept by it; if you’re not mic'ed, your voice will be carried by the wind (since sound travels on the air) in the direction of your audience, not away from it.
Microphones: Speaking of mics, your voice will be best picked up by it if you’re facing straight ahead—the moment you turn your head, even if you’ve got a lavaliere pinned to your chest, your amplification will drop. When you feel the need to address people on the sides of the room, turn from the waist, so the alignment of your face to the mike remains the same.
Voice: Even if you are mic'ed (but especially if you aren’t), projection is key. As they say in the theater: speak so that the people in the back of the room can hear you.
Distractions: Ignore them if you can; acknowledge them and continue when you can’t. If t’s a minor distraction like children crying in the distance, keep focussed on engaging your audience and making yourself inescapably compelling. If, however, there is a lizard crawling around on the face of your lectern--posing such a distraction that the audience can’t pay attention to what you’re saying—it’s time to lose the lizard, or welcome it to the event.
The Olde Globe Theatre in San Diego has an outdoor stage with the San Diego Zoo behind it. The San Diego airport is also nearby. The poor actors onstage—usually engaged in the already trying pursuit of performing in a Shakespearian play—have to contend with barking seals, the mating cries of tropical birds, low-flying aircraft, and the occasional fireworks display at nearby Petco Park.
They’d pause for the fireworks.