<Tr> <Th> Record high ° C (° F) </Th> <Td> 17.0 (62.6) </Td> <Td> 18.1 (64.6) </Td> <Td> 23.4 (74.1) </Td> <Td> 22.2 (72) </Td> <Td> 26.8 (80.2) </Td> <Td> 28.7 (83.7) </Td> <Td> 29.8 (85.6) </Td> <Td> 30.6 (87.1) </Td> <Td> 27.6 (81.7) </Td> <Td> 24.2 (75.6) </Td> <Td> 19.4 (66.9) </Td> <Td> 17.1 (62.8) </Td> <Td> 30.6 (87.1) </Td> </Tr> <Tr> <Th> Record low ° C (° F) </Th> <Td> − 15.6 (3.9) </Td> <Td> − 13.4 (7.9) </Td> <Td> − 9.4 (15.1) </Td> <Td> − 7.2 (19) </Td> <Td> − 5.6 (21.9) </Td> <Td> − 0.6 (30.9) </Td> <Td> 1.8 (35.2) </Td> <Td> 0.6 (33.1) </Td> <Td> − 1.7 (28.9) </Td> <Td> − 5.6 (21.9) </Td> <Td> − 9.3 (15.3) </Td> <Td> − 14.0 (6.8) </Td> <Td> − 15.6 (3.9) </Td> </Tr> <Tr> <Td_colspan="14"> Source: Met Éireann </Td> </Tr> <P> Dublin has many landmarks and monuments dating back hundreds of years . One of the oldest is Dublin Castle, which was first founded as a major defensive work on the orders of England's King John in 1204, shortly after the Norman invasion of Ireland in 1169, when it was commanded that a castle be built with strong walls and good ditches for the defence of the city, the administration of justice, and the protection of the King's treasure . Largely complete by 1230, the castle was of typical Norman courtyard design, with a central square without a keep, bounded on all sides by tall defensive walls and protected at each corner by a circular tower . Sited to the south - east of Norman Dublin, the castle formed one corner of the outer perimeter of the city, using the River Poddle as a natural means of defence . </P>

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