If some part of your day involves 40min walk, we wouldn't comsider that a "walkable" city in the US. Is that a common commute walk elsewhere? With temperatures as they are now in the southern US and southern EU, I think it could quite realistically kill people.
40 minutes is not a particularly long walk for us in Europe (as a Brit I can still say that right?). Though if I was doing it every day for work I'd probably buy a bicycle!