Wine Industry Newsletter

Seasonal climate comparison 2024 update

The climatic data of the current growing season in comparison to the previous seasons across WA’s 9 wine regions has been summarised by DPIRD technical officer Yu-Yi Liao.

This analysis offers wine producers insights into the similarities and differences between the current and previous growing seasons.

The graphs below illustrate monthly rainfall and accumulated rainfall from June 2021 to April 2024, followed by a comparison of accumulated growing degree days (GDD), average monthly temperature between the last 3 growing seasons, and daily rainfall for the current season.

This summer marked the warmest on record in WA since 1910 (BOM, 2024). Across all regions, there has been a substantial increase in accumulated GDD units compared to previous seasons, particularly attributed to above-average spring temperatures.

Reviewing the 3-year rainfall data, all regions experienced lower accumulated rainfall in 2023-24 compared to the previous 2 seasons. This is primarily due to the low rainfall recorded in October, March and April in 2023-24.

Growing degree day (GDD) unit calculation: the average daily temperature minus 10 when it is higher than 10°C; temperature lower than 10°C is counted as 0.

Accumulated GDD is the accumulation of GDD units from 1 October to 30 April.

Swan District

Figure 1 and 2 show data collected from the BoM Millendon weather station (site number 9281) representing the Swan District wine region. 

Swan District recorded the lowest accumulated rainfall among the 9 regions during the current season.

The 2023-24 season rainfall started high in June, then gradually declined throughout summer except for a slightly higher amount in September than the previous 2 seasons; overall, the current season finished 165 mm lower than the previous season.

Graph of rainfall for Swan District season 2021-24
Figure 1 Swan District 2021-24 season monthly rainfall and accumulated rainfall

Unseasonal heat in October and November resulted in an early acceleration of accumulation of GDD in the 2023-24 growing season, totalling 2,977 units, exceeding the previous season’s accumulation by 505 units.

Graph of Swan District growing degree days and daily rainfall
Swan District 2021-24 growing degree days and monthly average temperature comparison between 3 seasons, and daily rainfall in 2023-24

Perth Hills

Two stations were used to represent the Perth Hills, BoM station Bickley (site number 9240) and DPIRD station Glen Eagle in figure 3 and 4.

Winter rainfall in the current season was notably lower (by 110 mm) than in the previous 2 seasons.

Interestingly, January 2024 recorded 26 mm of rain, contrary to the typically dry summer conditions observed in most other regions.

Graph of Perth Hills monthly and accumulated rainfall
Figure 3 Perth Hills 2021-24 season monthly rainfall and accumulated rainfall

Perth Hills experienced a similar trend of GDD accumulation with slightly cooler temperatures compared to Swan District.

By the end of April 2024, accumulated GDD marked 2,656 units, which is 550 units higher than the previous season.

Graph of Perth Hills growing degree days and temperature comparison
Perth Hills 2021-24 growing degree days and monthly average temperature comparison between 3 seasons, and daily rainfall in 2023-24

Peel

Peel’s data in figure 5 and 6 is sourced from BoM Dwellingup weather station (site number 9538). Both 2022-23 and 2023-24 experienced a dry spring (137 mm and 155 mm respectively) compared to 2021-22 (303mm rainfall). Meanwhile, the 2023-24 season saw notably lower rainfall during November, December, March and April.

Graph of Peel monthly and accumulated rainfall 2021-24
Peel 2021-24 season monthly rainfall and accumulated rainfall

The accumulated GDD for the current season reached 2,401 units, which is 496 units higher than the 2022-23 season. There was also a noteworthy 36mm rainfall event on 17 January, similar to that observed in the Perth Hills region.

Graph of Peel growing degree days and average temperature
Figure 6 Peel 2021-24 growing degree days and monthly average temperature comparison between 3 seasons, and daily rainfall in 2023-24

Geographe 

DPIRD’s weather stations' Capel, Donnybrook and Dardanup 2 were compiled to represent Geographe in figures 7 and 8. 

The low rainfall experienced in July 2023 impacted total winter rainfall for the season and from October 2023 little rainfall was experienced as illustrated by the plateauing trend line in figure 7.

Graph of Geographe monthly and accumulated rainfall
Figure 7 Geographe 2021-24 season monthly rainfall and accumulated rainfall

Accumulated GDD totalled 2,494 units by the end of the 2023-24 growing season, which is 516 units higher than the previous season and 376 units higher than 2021-22.

Graph of Geographe growing degree days and temperature comparison
Figure 8 Geographe 2021-24 growing degree days and monthly average temperature comparison between 3 seasons, and daily rainfall in 2023-24

Margaret River

Figure 9 and 10 illustrate Margaret River’s seasonal data from DPIRD’s Vasse, Wilyabrup, Margaret River, Rosa Brook and Karridale weather stations.

The winter rainfall pattern in the 2023-24 season mirrored that of the previous 2 seasons.

October rainfall across the 3 seasons showed 2023-24 to be significantly lower and this trend continued throughout the following months.

Graph of Margaret River monthly and accumulated rainfall
Figure 9 Margaret River 2021-24 season monthly rainfall and accumulated rainfall

The accumulated GDD reached 2,158 units by the end of 2023-24.

The warm conditions during spring significantly affected early accumulated GDD, and this trend continued throughout the rest of the season.

Graph of Margaret River growing degree days and average temperature comparison
Figure 10 Margaret River 2021-24 growing degree days and monthly average temperature comparison between 3 seasons, and daily rainfall in 2023-24

Blackwood Valley

Data derived from BoM Bridgetown weather station (number 9617), DBCA station Styles Tower and DPIRD station Nannup are shown in figures 11 and 12.

In contrast to all other regions, accumulated rainfall from June 2023 to February 2024 followed a similar trend to the previous 2 seasons.

March and April in 2024 were unseasonably dry but overall, the total rainfall for 2023-24 was not all that dissimilar to the previous 2 seasons.  

Graph of Blackwood Valley monthly rainfall and accumulated rainfall
Figure 11 Blackwood Valley 2021-24 season monthly rainfall and accumulated rainfall

Figure 12 shows the 2023-24 season recorded a higher accumulated GDD (2,269 units) than the previous 2 seasons

October and November of 2023 were particularly warm, and few rainfall events occurred from December 2023 until the end of the growing season.

Graph of Blackwood Valley growing degree days and average temperature comparison
Figure 12 Blackwood Valley 2021-24 growing degree days and monthly average temperature comparison between 3 seasons, and daily rainfall in 2023-24

Manjimup

The BoM weather station at Manjimup (site number 9573) and DPIRD’s Manjimup HRS station provided data to represent Manjimup's growing season in figures 13 and 14.

Winter rainfall remained relatively consistent across the 3 seasons. The main variation occurred in spring, where the 2023-24 season experienced around 23% less rainfall than the previous 2 seasons. Additionally, March and April 2024 saw significantly less rainfall than previous seasons.

Graph of Manjimup monthly and accumulated rainfall
Manjimup 2021-24 season monthly and accumulated rainfall

The 2023-24 season accumulated 2,055 GDD units, which is 441 units higher than the previous season and 294 units higher than 2021-22 season.

Graph of Manjimup growing degree days and average temperature comparison
Figure 14 Manjimup 2021-24 growing degree days and monthly average temperature comparison between 3 seasons, and daily rainfall in 2023-24

Pemberton

The DPIRD Pemberton weather station was the only station used in figures 15 and 16.

Pemberton enjoyed high rainfall in June 2023 but showed a drying trend from October 2023.

The region tends to experience rainfall above 100 mm in April but received only 7.2 mm in 2024.

Graph of Pemberton monthly and accumulated rainfall
Figure 15 Pemberton 2021-24 season monthly rainfall and accumulated rainfall

As with all other wine regions, Pemberton also experienced a warmer 2023-24 season, accumulating 2,010 units of GDD by the end of April 2024. This total is 445 units higher than the previous vintage (1,566 units) and 285 units higher than the 2021-22 season (1,726 units).

Graph of Pemberton growing degree days and average temperature comparison
Figure 16 Pemberton 2021-24 growing degree days and monthly average temperature comparison between 3 seasons, and daily rainfall 2023-24

Great Southern 

Weather stations from the sub-regions of the Great Southern wine region were combined to produce figures 17 and 18.

The 2023-24 winter rainfall pattern was similar to 2021-22 and wetter than 2022-23; however, from October 2023, the current season rainfall trend was most similar to 2022-23 except for the low rainfall recorded in March and April 2024.

Graph of Great Southern monthly rainfall and accumulated rainfall
Figure 17 Great Southern 2021-24 season monthly rainfall and accumulated rainfall

Comparing data across all 9 WA wine regions, the Great Southern region had the least difference in accumulated GDD between the 3 seasons.

Accumulated GDD marked 1,876 units by the end of the 2023-24 season and is 194 units higher than the previous vintage and 421 units higher than the 2021-22 season. 

 

Graph of Great Southern growing degree days and temperature comparison
Figure 18 Great Southern 2021-24 growing degree days and monthly average temperature comparison between 3 seasons, and daily rainfall 2023-24

Summary of extreme heat days and heat waves over the past 3 seasons

The number of extreme heat days (defined for this article as 38°C and above) across the past 3 seasons is summarised in table 1; the data shows fewer extreme heat days in the 2022-23 season than in the other 2 seasons.

Table 1 Number of days with maximum temperature >38°C
Wine region 2021-22 growing season 2022-23 growing season 2023-24 growing season
Swan District 26 9 26
Perth Hills 19 3 18
Peel 11 1 12
Geographe 13 2 13
Margaret River 4 0 4
Blackwood Valley 7 0 13
Manjimup 6 0 7

Pemberton

6 0 3
Great Southern 2 0 3

Additionally, table 2 summarises the occurrences of heat waves, defined as 5 or more consecutive days with a maximum temperature of 35°C and above.

Interestingly, there are similar numbers of heatwave occurrences in seasons 2021-22 and 2023-24.

Worth noting, the Swan District wine region recorded a 10-day heatwave from 13 to 22 February 2022 and a 9-day heatwave from 7 to 15 February 2024.

Table 2 Number of heat waves
Wine region 2021-22 growing season 2022-23 growing season 2023-24 growing season
Swan District 3 3

4

Perth Hills 3 1 3
Peel 3 1 2
Geographe 2 0 1
Margaret River 1 0 0
Blackwood Valley 2 0 1
Manjimup 1 0 0
Pemberton 1 0 0
Great Southern 0 0 0

For further information on the data presented, contact Yu-Yi Liao.

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