I could use some help, especially if you have experience--
I will be running a marathon in Missoula, MT (3300 ft) in July. I live at about 600 ft. in Missouri. The race's website has a Q & A section where they say that altitude is not usually a factor for most runners in the race.
My personal situation-- I ran 1:24 in a half-marathon last fall and am building up to this full one. I chose the race for the cool temps and flat course (I wanted a summer marathon with both in a place I'd never been), but I'm now starting to wonder if the lower oxygen concentrations will affect my time. In years past I've run above 5,000 ft (felt a little different) and 7,000 feet (felt a LOT different). I'm shooting to break 3 hours, so I don't have many minutes to spare. A little research showed that the difference in oxygen concentration will be about 2%... 20.5% where I live and 18.5% in Missoula.
1. Will the altitude affect my performance? If so, how much?
2. Any advice on how to best get ready for the change? It's hot and hilly where I live, so I'll be training with that regardless. I cannot get there earlier than the day before.
Thanks in advance for any help you can offer!