You won't get a warning that a strike is imminent because the lightning event from cloud to ground and back occurs faster than you can blink an eye, so stay in the lightning position until the storm passes. This position reduces the chances of lightning injuring you as badly as if you were standing, but is no substitute for getting to safer terrain if it is immediately available. A dangerously close strike actually offers a moment of opportunity to move, while the electrical field rebuilds itself. But in wide open country or gentle rolling terrain there are no simple terrain advantages, so use this position to reduce exposure. If you are concerned enough to use the lightning position, have your group dispersed at least 50' apart to reduce the chances of multiple injuries.
Lightning can strike at any time of the day.
Plan on hiking back down the trail before the afternoon rolls around, and even earlier when hiking in the tundra. As you're hiking, look up at the skies every 15 minutes and know how to read the ever-changing weather conditions. Again, if you hear thunder and are above treeline, turn back immediately. If you see dark clouds with flat bottoms developing, it's a good sign that thunderstorms will develop and it's time to head home. Stay alive and come back to hike the trail another day.