it is difficult to really experience or “feel” the size of the United States . To get the full impact you should realize , for example , that it takes 48 hours (two entire days and two long nights) to travel by train from Chicago to Los Angeles , rolling along hour after hour across wheat fields , mountains , and deserts . Another way to think about it is to compare distances in the United States is also one of great extremes . From New England and New York thourgh Chicago and much of the Midwest and Northwest , temperatures vary from subzero in winter to the high 90s (Fahrenheit) or over in summer The South and Southwest have warmer weather , though even these sections have occasional frosts and priods of moderate cold . Generally , summers are likely to range from 70F to 100F (21C to 38C) , and many areas can be quite humid . However , air conditioning is so widespread that you can expect most office buildings and homes to be kept at relatively comfortable temperatures