1. Rain Advice
Rainy months in Orlando are June through November, which coincidently just so happens to be hurricane season. If you plan on visiting a theme park during these months, it is suggested you take an umbrella with you or a rain poncho.
Rain Ponchos are a great option for the theme parks, easier to pack and they tend to provide more flexibility when moving about on rides and shows. I always keep one on me, flattened down and stored in a zip lock plastic bag - tight and compact. If it does rain, just fold the plastic poncho back up after use and restore in the baggie - to prevent your bag from getting soaked. It is unfortunate to have your day ruined by an unexpected downpour - and both umbrellas and plastic rain ponchos, which can usually be purchased at a dollar store, can be quite pricy at the theme parks.
2. Protect Valuables
A big fan of zip lock baggies, I tend to always keep a few in my bag. When the kids were younger, I would keep them for leftovers that could be stored and pulled out later when the munchies struck. I now find this is a great way to keep items organized in my bag and more importantly, a great way to protect valuables such as a cell phone, camera or the car remote when a rainstorm strikes or for water dousing rides.
3. Keep the Car Cool
If you are parking at a theme park for the day, consider picking up a car sun shade. The inside of a closed up car sitting in a black asphalt parking lot for 8 hours can easily reach 10 - 20 degrees higher than the outside temperature. This tip is especially important for Orlando during the months of May through October.
4. Quench Your Thirst
Staying hydrated is very important during the brutally hot summer months. In Orlando, summer runs pretty much from May through October. It is recommended to bring a water bottle with you when visiting a theme park. If you are visiting a park that does not allow outside food and drink, most restaurants will provide a cup of water free of charge - just be sure to mention that you want a cup of ice water, else you may be charged for bottled water - which often times can cost more than a soft drink. Another idea is to bring individual packages of dry gatorade or other powder mix that contains electrolytes that can be added to water.
5. Comfort First for the Feet
Dress for comfort - especially with comfortable walking shoes. There will be a lot of walking and standing at the parks, so be sure your feet are comfortable. If you think there is a chance of a heavy rain or you are the type to brave the water dousing rides then you may want to consider a good pair of walking sandals (not flip flops). I know this seems obvious, but a heavy rain can make for sloshy shoes that could last for the entire vacation. The parks are very strict 'shoes required' and if you happen to lose a flip flop on a roller coaster or due to heavy rain, you may be required to purchase a pair of shoes at one of the stores or leave the park.
6. Sun Screen, a Necessity
Remember that even if it looks overcast, you can still get a sunburn and it doesn't take hours of walking around in the Florida sun to get burnt. Always apply sunscreen to the face, chest, shoulders, head (including the tops of the ears) - basically, any exposed part of your body. It is especially important to remember babies, young children and elderly people who may be more fair skinned. If you are at the park for the whole day, be sure to bring some lotion with you to reapply with throughout the day. It's also not a bad idea to wear a loose fitting long sleeved cotton shirt and hat for extra protection. More on Sun Protection.