Thanks for all the replies, much appreciated. I've lived in Chiang Mai part time for several years and am a guide book fiend, but I guess I was in denial, or just underestimated how bad it would really be!
My friends and I continued our trip and thankfully, things improved. Nong Khiaw was the absolute worst. I'm not exaggerating when I say that it was almost impossible to spend any period of time outdoors, especially after 2 or so. After we got to Muang Ngoi we had intermittent rain for a couple of days, which helped a lot. It washed out the air, and I think the ground saturation made it impossible for farmers to burn fields for a few days. Things got better as the trip progressed.
@larsay, as a matter of fact I am a history buff, and have wanted to visit DBP for many years. I brought a copy of Bernard Fall's Hell In A Very Small Place, which is a long, very detailed account of the battles there. DBP is indeed a small place, or at least it was at that time. The battle sites have very little info posted in English but thanks to the book I was able to understand what actually took place at those spots, many of which are right in the middle of town. Very interesting visit for me. Very, very sad story there.
Not knowing what the air would be like in Sapa (which I was curious about, but didn't have my heart set on) and Ha Giang (which would have involved a lot of long mountain roads)we bailed out and flew to Nha Trang via Hanoi to enjoy some beach time. I'm here now and the air is crystal clear. The 2 daily flights from DBP to Hanoi were cancelled for 2 days due to poor visibility and by checking Flightradar, we saw that many flights had been cancelled in the previous weeks as well. I don't know if that was due to smoky air, cloud cover, or both.
@Chiang_Mai, yes, my wife and I read that CM at the time of my initial post had the worst air pollution in the world! That's a pretty sad label for what I consider to be my new "home town". We also read that schools were closed for a few days. I plan to be back a week before Songkran and I hope things will be better. I do a lot of bike riding around CM and don't mind the heat much, but would never do a long ride in the kind of pollution that we saw last week.
I was in CM for Songkran about 5 years ago and the air was fine, but the consensus seems to be that this year is extra bad in this part of the world. I hope that was just a fluke, but maybe it's not. I, my Thai wife, and our friend spent a lot of time discussing the pollution problem and what the future might bring. It's a regional problem that goes back many decades, worsened now by fossil fuels and industrial pollution. I don't know that if there are any solutions coming, though I see more natural gas vehicles and electric bikes in Thailand now, which offers a little hope.
