What is the grasshopper and the cricket basically trying to say?

In my opinion, the meaning of this poem is that life goes
on at all times and in all circumstances and that there is some aspect to life that is
always beautiful.  The poem is actually literally talking about nature, but I think that
you can see it as applying to human life as well.

In the
poem, beauty can be found no matter whether it is too hot for birds (things that we
usually think of as beautiful) or too cold for just about any life.  In both cases,
things seem bad, but there are still these things (the cricket and the grasshopper) that
make life beautiful.

By analogy, you can say that there are
times in our lives that may seem bleak, but if we look hard enough, we can find things
that are beautiful and should give us hope.