There are 4 weather conditions that will keep us on the ground.
High wind
Wind is a balloons biggest enemy. Wind of more than about 10mph will make the balloon almost uncontrollable. We do not like to take passengers if the winds are more than 6 MPH.
To put a balloon up you must first fill it with air. This is done by laying the balloon on the ground and starting a large fan. You must hold the balloon still long enough to fill it with air before you turn on the burner to stand up the balloon. If you have any wind the balloon will begin to catch the wind like a giant sail and begin to drag itself across the field. A balloon can generate as much as 6,000 lbs of pulling force in as little as a 12 mph wind. At this time we don't even want to talk about landing in windy conditions.
Poor Visibility
A Hot Air Balloon is a VFR type of aircraft. This means Visual Flight Rules. These are rules written by the Federal Aviation Administration. Not only is it illegal to operate a balloon in poor visibility but imagine driving your car with your eyes closed. You're bound to hit something and it wont be pretty. To land a balloon the pilot must slow the decent of the balloon to get it to level off right at the ground level. Hard to do when you can not see the ground. We also need to have room under the clouds to fly. If the clouds are only 1,000 feet off the ground we do not have the legal distance requirements to fly. Keep in mind, there is a delay between when the pilot turns on the burner and the balloon begins to respond. Very much having a deer run out in front of your car on the highway. By the time you see the deer its too late. Remember also that in poor visibility other aircraft can not see us either. If there is even a chance of visibility issues we will choose not to fly. This is (in our opinion) the most dangerous condition.
Wind Shear
There are days when it seems perfectly flyable on the ground. BUT.. In some cases the wind just above the tree tops is scooting along real good. This is what we call a "Wind Shear". There are several problems with high winds aloft. First is that your ground team can not keep up. The recovery team must travel about 2.5 times faster on the ground that you are flying in the sky in order to keep up. The balloon is going cross country and the ground team is on roads that may not go parallel to the balloons flight. On the ground they must deal with turns, stop lights, Stop Signs and 
TRAFFIC. If you are flying along at 25 miles per hour they must be doing 62.5 constantly to keep up. Another problem and more severe is what the shear does to the balloon. Lets stop for a second and explain a shear. This is a point in the sky where two different layers of wind have A). a significant speed difference or B), a considerable difference in direction. When a balloon hits a wind shear it can collapse the side of the balloon causing the pilot to burn thru the skin of the balloon or the balloon can literally skip off the shear like a rock on water.
Think of it like this.
Here is a great analogy: Imagine we have placed a hula hoop about 250 feet out in a lake. You have a rock and you have to skip the rock off the water and make it stop inside the Hula Hoop. Sounds nearly impossible, Now, You get one chance at it and your betting your life on it. We won’t do that. Flying a balloon when there is a significant wind shear at low levels to the ground is simply not safe.
Rain
Generally when you have rain you have weather conditions that can change dramatically. Here in Florida rain is either driven by an advancing cold front or by the convective heating of the surface of the earth by our intense sunshine. In either case the rain on a balloon will add dramatic weight to the skin of the balloon forcing the pilot to add extra amounts of heat to keep the balloon aloft. It is possible for this weight to become so heavy that it literally forces the balloon into the ground. If the pilot can successfully land the balloon the damage to the fabric of the balloon will completely ruin the aircraft. WE DO NOT LIKE RAIN.
As we like to say:
"We have 100 reasons WE WANT TO TAKE YOU FLYING. We only have one reason we will not. SAFETY".
"I hate to disappoint someone but I refuse to hurt anyone"
A quote from a famous flight instructor
