In act 1, scene 3 of William Shakespeare's historical tragedy Julius Caesar, Casca, a Roman nobleman and tribune, and Cicero, a Roman senator, meet in a street in Rome during a raging thunderstorm. Casca seems awestruck by the storm, and he tells Cicero that he's seen many storms in his life, but he's never seen such a violent storm with so much lightning—what he calls "a tempest dropping fire" (1.3.10).
Casca thinks that the storm signifies unrest among the gods, "a civil strife in heaven" (1.3.11), or some wrong done to the gods by the Roman people which has caused the gods to send such destruction on them.
Cicero also seems awestruck by the storm, but in a positive way, asking Casca, "Why, saw you anything more wonderful?" (1.3.14).
Casca then describes to Cicero what he's seen that evening which causes him such concern and distress. Casca says that he saw a slave who held up his hand, "which did flame and burn / Like twenty torches join'd" (1.3.16-17), but his hand remained unharmed. A lion brushed again him in the Capital, Casca says, but it passed him by without attacking him.
Casca tells Cicero that he saw a crowd of a hundred fearful women, "who swore they saw / Men all in fire walk up and down the streets" (1.3.24-25). Casca also says that he saw an owl, "the bird of night" (1.3.26), sitting in the Forum marketplace at noon, "howling and shrieking" (1.3.28).
Casca believes that these are unnatural, unexplainable occurrences, "portentous things" (1.3.32), which reflect the current state of unrest in Rome and which are omens foreshadowing tumultuous events in the city.
Cicero remarks that the state of Rome does seem to be unsettled at the moment, but "men may construe things after their fashion" (1.3.35), meaning that people will perceive and interpret these events based on their own frame of mind and their own frame of reference, which might have nothing at all to do with the events themselves.
Casca's belief is that these events portend upheaval and chaos in Rome, but for Cassius, who Casca next meets in the scene, the terrible storm will pass, and—with Caesar's assassination—Rome will be cleansed of its "yoke and sufferance" (1.2.90), and the tyranny of Caesar's rule over the city will come to an end.