What is happening in the natural world the night that Duncan is murdered in Macbeth? Elizabethan England believed...

On the night that King Duncan is murdered, there is a
terrible storm outside and many strange sounds are heard.  When Macduff and Lenox arrive
at Macbeth's home, Lenox tells of the night
happenings:

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"The night has been unruly:  where we lay, our
chimneys were blown down; and, as they say, lamentings heard i'th'air; strange screams
of death, and, prophesying with accents terrible of dire combustion, and confus'd
events, new hatch'd to th'woeful time, the obscure bird clamour'd the livelong night: 
some say, the earth was feverous, and did shake."
(II.iii.53-59)

The unsettled
nature of the environment suggests that something out of the natural order has
occurred.  Further, just before Macbeth reports to Lady Macbeth that he has gone through
with the murder, she mentions the shriek of the owl:

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"It was the owl that shriek'd, the fatal bellman,
which gives the stern'st good-night."
(II.ii.3-4)

The owl is also
an element of nature that suggests that something is amiss, particularly that
something/someone has died ("good-night").  Shakespeare has used these elements of
nature as symbols to represent the death of King Duncan and to foreshadow the disorder
that will be brought to Scotland under the rule of Macbeth.