Hard to tell! You could be affected by storms and heavy rain.
If a storm does arrive, do you have access to sturdy shelter? By sturdy shelter I mean a building with plumbing/electrics. Tents, marquees etc provide no protection from lightning. In a pinch retire to cars if that is possible.
Bear in mind though that thunderstorms can bring down trees due to high winds and sometimes create large, damaging hail. This may be possible during some of todays storms.
Theres a very, very rough guide to when to get indoors. If you count 30 seconds or less between lightning and thunder, then the storm is close enough to be dangerous. Seek immediate shelter. Stay in the shelter until 30 minutes after the storm has passed.
If there genuinely is no shelter, seek low ground. Get off hills and ridges. Be careful of the risk of flash flooding though, so avoid gullies. If in woodland, find lower clumps of trees rather than tall ones. Note that this isn't a safe option, it is a safer option. Avoid wire fences and electrical wires/pylons. Spread your group out. (But don't leave kids to stand alone to achieve this, poor loves!)
If it feels very close and you have got to as safe a location as possible, then either assume the lightning crouch, or sit on rucksacks, with feet on them. Do not lie down!
As you can imagine, I'm someone who believes that organised groups should have severe weather policies, ready to implement when severe weather threatens. People don't always act safely or logically in the heat of the moment. It also removes the fear factor, if organisers can be seen to know what to do.