The T5 will be fine; don't worry. The T-5 10w-30 and T6 5w-40 have essentially the same cold pump properties, BTW.
For reference, last year it got down to -17F (ambient, not windchill) here in Indy. My 2006 Dmax (on original batteries) started and ran just fine on dino 10w-30 Rotella. The UOA last year showed no issues whatsoever from those several days of cold starts.
People overthink the 5w v 10w topic. If you saw routine cold starts below -25F, all the time, then it might be worth the concern. But for a trip, you've already got a great lube in there. Use it.