Trip to/from Oshkosh EAA Airshow. July 30 Flew from Everett, Wa. ( Paine Field ) to Billings, Mont. ( Billings-Logan ) I took off IFR around 22:00 Z, and flew V-23 towards Seattle. Seattle center turned me off at an angle to intercept V-2. Around Mulligan Pass I started noticing a line of thunderstorms and Virga all the way to the ground about 30 miles to the north of me. During my briefing I was told about a line of thunderstorms about 50 miles north of my route, so I was ready for them. It is most impressive to see lightning strikes as long as they are miles away. I kept aware of all the small airports and clearings that I could reach to the south if the weather deteriorated along my route of flight. I was not worried since there was plenty of VFR conditions to the south. Around Missoula I ran into some stray CumuloNimbii and requested deviation to the south, the controller said I could but I'd have to jump up to 12000, this I did, and after a few minuites was clear of the weather and back on V-2 at 11000 feet. Around Helena I started to run into a brown layer of smoke from all of the forest fires in the area. The air got so bad that I eventually requested 12000 so I could breath better, I did check my fingernails for any signs of hypoxia, but they didn't turn blue. By the time I got to Livingston VOR I was more than ready to quit for the day, there was still a solid line of thunderstorms to the north, and several lightning strikes visible as I was vectored to the ILS for rwy 9L at Billings. While shooting the approach in VFR conditions, I like to shoot approaches to unfamiliar airports even though the conditions might be VFR, I noticed a small fire that appeared to the north of my course a few minuites after a particularly spectacular lightning strike. After landing and getting a complimentary pickup from a local hotel I was done flying for the day after 5 hours and 12 minuites of flight. A personal record both for longest leg of a flight and total flight for a day. July 31 Flew from Billings, Mont. ( Billings-Logan ) to Bismark, N. Dak. Took off around 16:15 Z again IFR. I cruised at 9000 and arrived