[M T]

And remember - October in Germany is rather cold. 
There are a lot of places in the USA that won't see coronavirus friendly conditions like that until November with numbers emerging in December.
Octoberfest traditions in Germany, even if dramatically cut down, could show big numbers in November.
Thanksgiving traditions probably will appear in the USA numbers in December.
Therefore, better to measure fall/winter success relative to another place by March 31 2021 rather than day to day.

As part of my trying to get some estimate of the number of virus particles one might inhale, I looked at what happens to the cloud of particles you exhale.  I was struck by how fast the condensation rises (see the first 2 seconds of Vimeo video 69391280) when you're in near-freezing weather.  In freezing weather, unless someone is right in your face, they won't inhale any particles you breath out, at least not until after that cloud goes well above your head, cool and then falls down again (giving plenty of time for dissipation).

I also looked at what happens when someone exhales smoke.  That cloud, when indoor, doesn't rise very fast. It seems smokers rarely exhale normally, but there is an almost normal breath of a smoker (emphasized, but not blown) at 3:15 of the Youtube video tOOkWk9tsDI (I don't want to give it a link!) where you can see the smoke doesn't rise anywhere near as fast.

I wouldn't be worried about inhaling someone else's exhalation in the cold of winter outdoors.  I would be more worried during the summer.  I don't know if the difference between indoor temperatures of 68 in the winter vs 78 in the summer will significantly affect convection of a 98-degree exhalation.  Any difference may be offset by what I suspect is increased air movement indoors in the summer.

The tidal volume of a normal breath is about 0.5 liters, which is about the size of a 4" diameter sphere.  If a mouth breather is emitting 0.1 micron-sized particles per second (Asadi study), that's about 0.7 particles per exhalation (each having 250 virons), you'd need to be around them quite a while OR be unlucky without a mask to inhale two such particles to get to an infectious dose.   As that breath diffuses into the surrounding air (to, say, a 1-foot or 2-foot spherical volume) the likelihood drops, especially if convection takes it above your head.

OTOH, if you go into a closed environment where an infected person has been breathing (talking, exercising, etc.), without enough air replacement, then you may be receive an infectious dose almost immediately.

And, by the way, when someone is walking at a normal pace, they exhale about every 18 feet.  Likewise, you'll inhale that often.  If you're walking perpendicular or toward them, you're highly unlikely to breath any of that 4" sphere.   If you're following them, you would sometime inhale near where they exhaled, but like two watches running at slightly different speeds, you are unlikely to do that more than once in a long while.

[M T]

And remember - October in Germany is rather cold. 
There are a lot of places in the USA that won't see coronavirus friendly conditions like that until November with numbers emerging in December.
Octoberfest traditions in Germany, even if dramatically cut down, could show big numbers in November.
Thanksgiving traditions probably will appear in the USA numbers in December.
Therefore, better to measure fall/winter success relative to another place by March 31 2021 rather than day to day.

As part of my trying to get some estimate of the number of virus particles one might inhale, I looked at what happens to the cloud of particles you exhale.  I was struck by how fast the condensation rises (see the first 2 seconds of Vimeo video 69391280) when you're in near-freezing weather.  In freezing weather, unless someone is right in your face, they won't inhale any particles you breath out, at least not until after that cloud goes well above your head, cool and then falls down again (giving plenty of time for dissipation).

I also looked at what happens when someone exhales smoke.  That cloud, when indoor, doesn't rise very fast. It seems smokers rarely exhale normally, but there is an almost normal breath of a smoker (emphasized, but not blown) at 3:15 of the Youtube video tOOkWk9tsDI (I don't want to give it a link!) where you can see the smoke doesn't rise anywhere near as fast.

I wouldn't be worried about inhaling someone else's exhalation in the cold of winter outdoors.  I would be more worried during the summer.  I don't know if the difference between indoor temperatures of 68 in the winter vs 78 in the summer will significantly affect convection of a 98-degree exhalation.  Any difference may be offset by what I suspect is increased air movement indoors in the summer.

The tidal volume of a normal breath is about 0.5 liters, which is about the size of a 4" diameter sphere.  If a mouth breather is emitting 0.1 micron-sized particles per second (Asadi study), that's about 0.7 particles per exhalation (each having 250 virons), you'd need to be around them quite a while OR be unlucky without a mask to inhale two such particles to get to an infectious dose.   As that breath diffuses into the surrounding air (to, say, a 1-foot or 2-foot spherical volume) the likelihood drops, especially if convection takes it above your head.

OTOH, if you go into a closed environment where an infected person has been breathing (talking, exercising, etc.), without enough air replacement, then you may be receive an infectious dose almost immediately.

And, by the way, when someone is walking at a normal pace, they exhale about every 18 feet.  Likewise, you'll inhale that often.  If you're walking perpendicular or toward them, you're highly unlikely to breath any of that 4" sphere.   If you're following them, you would sometime inhale near where they exhaled, but like two watches running at slightly different speeds, you are unlikely to do that more than once in a long while.