Yes. The danger to you is a battery explosion. Batteries contain hydrogen gas, which can ignite and explode if a spark occurs anywhere near the battery. Batteries also contain acid which may be splashed on you if the battery explodes.
The danger to your vehicle is if someone reverses the jumper connections or touches the jumper cables together. The voltage surge that results may damage your charging system and/or other electronic components in your vehicle.
To minimize these risks, use the following procedure when jump :
CAUTION: DO NOT make the final jumper connection directly to the low or dead battery itself.
The reason for not doing this is because the final jumper connection usually produces a spark. Making the final connection away from the battery will minimize any danger of an explosion by keeping the spark well away from the battery.
If the vehicle does not crank or cranks slowly, recheck the jumper connections. If it still doesn't crank, the problem may be something other then the battery (such as a bad starter, solenoid, battery cable connection or internal engine problem).
If the vehicle cranks normally, but refuses to start, it may have an ignition, fuel or mechanical problem.
Do not crank the starter more than thirty seconds at a stretch. Allow the starter to cool for about two minutes before cranking the engine again. Continuous grinding of the starter can cause it to overheat and fail. Continuous cranking can also sap the juice out of your good battery and/or overload and possibly damage your charging system, too!