So, it's been cold in the midwest. Actually it's really never been consistently this cold outside of Duluth and this means when jumping a dead car it's not a bad idea to consider if the battery is frozen.
So what are the best steps to check for this? Around what temperatures is the to be expected at a reasonable charge, eg the car started when it was 15*f warmer? After an actual freeze can the battery be used again, or must it be replaced?