Origin of the smoke/haze?

Farmers burning their fields before planning.

Too early for planting.  Plus last year Jalisco banned burning of fields and it was pretty well enforced.  

OP--by webcam, to you mean the one at ajijicweather.c0m?  All I see on my daily walks on Ajijic malecon is a lot of evaporation haze.

Here's lakecam shot from a few minutes ago.  You can see the evaporation as it rises from the lake surface.  At that site you can also look at video of cam over a day or a week.  

Yes; the drier the weather, especially when there is little breeze, you are likely to see the haze of lake evaporation hovering over the lake, and even up the slopes along the shoreline. Lake Chapala's greatest water loss is due to evaporation.

Banned or not, they are still burning. And there may be forest fires; it is the dry season. Smoke travels a long way and ends up stuck in our mountain range blow quite often.

But surely one can tell the difference between smoke and haze, right?

Evaporation haze, been happening for as long as I can remember.