Check this out: see how the Eiffel Tower is barely visible in this photo? That's because of the high levels of smog that have covered Paris and other areas of northern France.
A similar phenomenon happened last year. Then and now, officials took emergency measures including lowering speed limits and banning trash fires to try to prevent even more pollution from building up.
What's causing the smog to build up? There's a high pressure area that's preventing pollutants from escaping and leading to a murky haze as seen in these photos.
This is really dangerous to those in the city: the particles can cause problems for people with sensitive lungs and compromised immune systems. The safe limit for these PM10 particles is 80 micrograms per cubic meter. You can see the levels right now above, and check them for updated levels here. If you've got travels planned, make sure to stay updated and prepare accordingly!