It commenced on the 8th July, 1997 when an all time record low was established with a minimum of 0.4 C, breaking the old record of 1.2 C back on the 7th July, 1916. This was broken again three days later with 0.2 C and then Perth City's first official freeze and new all time record low of 0.0 C occurred on the 15th July, 1997.
The cold nights lasted for 16 days, with six of those nights having temperatures under the old 1916 record of 1.2 C.
A large high pressure system which brought clear skies and light winds was responsible for the cold nights and gave fine, sunny and cool to mild days.
Here is the daily minimums for Perth City during the cold snap in 1997.
8th July 0.4 C 9th July 3.9 C 10th July 0.9 C 11th July 0.2 C 12th July 1.9 C 13th July 6.7 C 14th July 2.2 C 15th July 0.0 C 16th July 3.7 C 17th July 1.3 C 18th July 0.5 C 19th July 1.9 C 20th July 1.0 C 21st July 1.6 C 22nd July 1.8 C 23rd July 6.3 C
Another record occurred on the 11th August when the temperature fell to 1.4 C, which beat the old August minimum record of 1.8 C on the 31st August, 1908.
It must be noted however, that the official Perth City site moved in 1993 to nearby Mount Lawley, and since that time it has been showing colder overnight minimums than the old site during winter. Click here for information on Perth's previous observing sites for the city.