2020 annual weather review

The annual review of the weather at Ferny Grove during 2020 is now available.

The summary containing the key information can be found here.

The full report of more detailed analysis is available here.

In 2020 at Ferny Grove the annual mean temperature was 0.6 ºC above average and the second highest on record behind the current high in 2019. Overnight temperatures in 2020 were also the second highest on record and highest since the current record high of 15.7 ºC in 2010 (0.6 ºC above average). Daytime temperatures were above average at 0.8 ºC above average and was the lowest since 26.7 ºC in 2015.

There were several hot spells during January and February for both overnight and daytime temperatures. The lowest temperature in both months was the highest in 10 years. In March and April above average temperatures persisted but became less frequent, though there were very few cool days in April (the highest on record for April). Warm days continued into May though there was a cold day on the 23rd that was 9 ºC below average. During winter temperatures were generally above average with comparatively few cool nights with many warm nights as well as very few cool days that included a spell of warm days in the first 18 days of June.

The lack of cool nights continued in spring with the coolest night in October being record high before cooler nights and overall below average overnight temperatures in November with a distinct lack of rainfall. Daytime temperatures started in Spring that were close to average, became above average in October and eased back to near average in November. Warm nights then returned in December, though daytime temperatures were generally close to average.

From 11 years of temperature measurements at Ferny Grove annual mean temperatures in 2020 continued a rising trend of the 5 year rolling mean temperature rising from 20.9 ºC in 2014 to 21.4 ºC in 2020, albeit slowed a little compared with 2019. Mean annual maximum temperatures have been rising year-on-year and is 2 ºC higher compared with 11 years ago but have eased a little in 2019 and 2020. Annual mean minimum temperatures have shown a general slight rise in the last 11 years.

Rainfall during 2020 was near average with a total of 1135.5 mm (104.4% of the long term average and much higher than the well below average rainfall total of 581 mm in 2019. The highest daily total rainfall was 93.9 mm on the 7 February during an active period of showers, thunderstorms and rain during most of the month. The rainfall total for February was the highest since 1995. After well above average rainfall in January and February, rainfall eased in Autumn and was below average in April and May with May being the driest since 2004. A severe thunderstorm on 6 March produced 40 mm in 30 minutes.

After near average rainfall in June, July was the wettest since 2012 before below average rainfall in August and September. Later in October was an active period of thunderstorms that included a severe thunderstorm that brought 14 mm of rainfall in 8 minutes and marble size hail on 25 October. November was record dry exceeding the record set in 2019 with a mere total of 4.7 mm. Rainfall in December was near average with an active period of thunderstorms during the middle of the month and was the wettest December in 10 years.

Long period rainfall at Ferny Grove in 2020 improved from the large deficiencies in 2019 but remain below or well below average for periods longer than 12 months and was near or above average for 6, 9 and 12 months. This is a consequence of an on-going multiple year trend of below average rainfall beginning in late 2017.

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