From today I have exactly 21 days for the race in Mexico. The weather here in Northern Europe is getting fu… cold and dark 
and the question is should I train outside or inside?
There are many aspects into this.
Since I came home from Fuerteventura and the sportsresort of Playitas, I have been trying to balance the weather and training.
How do I choose (well my programme makes some of the choices for me !)
– generally I like to be outside. I like to adapt to the nature/weather, and I belive it is part of Ironman, that it is an outdoor event.
– is the weather racespecific ?? I will race next time in Cozumel, it is hot, humide and some wind from the side on the bikecourse. So… I look for that. I got the heat and wind on Fuerteventura, this is good.
– the fase I am at the moment, 3 weeks from the race, I think a lot of the effectivenes of my training. (always do, but even more now)
It does not help going to Mexico, if I cannot push myself to the limits, as my goal for the race is pretty high 
and here comes the indoor training in play at the moment, like running on the treadmill, = hot and gives a good legfrequevens. And if I do my long run here, it is really a mental-terror session for me. I go without music, look into the wall, alone in the local gym, and focus for 2 hours on my tecnic. That is mental training hard-core for me, cause I really like to be outside, puuuuuuh-hahhhh!
– I have some key sessions on the bike, where there is intensity to be made, for specific time/speed/watts, and the hometrainer is just super for that. And again, it is really hot in our apartment, so good for the heat/sweat adaption.
– running… it is already pretty cold outside, you avoid injuries by training on the treadmil, that might occur from the chilly weather
– the heat is all the time a point to think about, so I also do sauna , and again, the run and bikerides inside are good also.
– and the most important : dont get sick by freezing in the temperatures, that are outside at the moment
The points above are something to think about when having a race at this time of a year. But remember, if you get sick couple of weeks before your race, dont get frustrated or miss the hope of racing, but count the days that you are sick as restitution. It is not your muscles that are sick they are resting, so you will be ready on the startline see you out there!