Currently the prime ministers of Slovakia, Poland, Czech Republic and Hungary, together with representatives from Austria, Croatia, Slovenia, Serbia, Romania, Bulgaria and Bosnia Hercegovina are meeting in Budapest to discuss alternative energysources. Due to this roads are closed down, and especially tomorrow as these guests will leave the nation the main road to the airport will be closed and this will make it a nightmare to get to and from the airport for everyone else!
There will also be quite some streets closed down in the center of Budapest during this period, and especially in the 5th district near the Roosevelt Square cars are not allowed to park.
This description is not to detailed, but the main point is that you should be aware of this, and if possible to avoid the inner parts of the 5th district today, and start your trip to Ferihegy tomorrow in good time before departure.
To avoid the traffic jams – use public transportation instead, and maybe grab a good bite in a Budapest restaurant!