They need to stay dry and they need to stay warm but not too hot. Until they feather out, rain or getting wet can chill a chick, thus they need to stay dry.
If the temperature, including night time temperature, does not get below the recommended temperatures for their age, they don't need a light. I'll mention the party line, which is 90 to 95 degrees the first week, then drop 5 degrees a week until you reach your regular temperatures or they fully feather out.
I do think they are tougher than we normally give them credit for. You can listen to them when the temperature drops and they will tell you if they are too cold by their peeping. They will sleep in a pile whether they are cold or not, but that does tend to keep them warm. My 28 could handle temperatures a little cooler than your 5 probably can. Those 28 put out a lot of heat on their own. Chicks too cool may live but they don't thrive as they would if the temperatures are right. And they can die if they get too cold, either from the chill or they are more likely to catch diseases since they are weakened.
Too much heat is worse than being a little cool. If they are in a cage outside in Florida this time of year, they need shade and plenty of water.
Editted to add:
They also need to be protected from drafts. They can chill in a draft. You can use a draft guard or keep them in the coop lile Cmom.