"When the sun is out and the wind is still, You're one month on in the middle of May" - Robert Frost
Following my late filing of April's report, I was keen to be a little quicker off the mark with May's. I think there is still room for improvement!!
My recollections of May were warm (without any especially hot days), sunny and dry though I may have been influenced in this opinion more by the end of the month than the beginning.
Photos 1, 2, & 3 show the view from the rear window on May 1st, 14th, and 26th. The white apple blossom was a feature of the first days of May (Photo 1) - Rev W Wilks and Golden Delicious to the left of the garden path and a crab apple next to the red acer.
Photo 1: Rear Garden View (May 1st)
By the middle of the month (Photo 2), the apple blossom had mostly gone to be replaced by the mauve wisteria flowers covering the archway to the kitchen garden and pinkish-white blooms of photinia in the distance. On the patio, the late-flowering Tulip Antoinette had moved into its salmon pink phase.
Photo 2: Rear Garden View (May 14th)
Coming to the end of May (Photo 3), the garden enters its verdant phase. There is still plenty of colour to be found but you have to look for it.
Photo 3: Rear Garden View (May 26th)
A slideshow of the daily photos has been collated in Video 1.
Video 1: Garden Slideshow - May 2023
Summary of Weather Parameters for May 2023
Cooling and Heating Degree Days have been added to the list. Sunshine hours are estimated from average daily solar radiation values measured by the Davis weather station. A list of average and total weather parameters is given in Table 1.
May 2023 was a middling sort of month with no extremes. Mainly dry (below average rainfall) and sunny with no frosts and relatively calm (no strong winds).
Table 1: Average/Total Weather Statistics for May 2023
May 2023
Weather Parameter
Value
Dates
Average Monthly Temperature
14 oC
Maximum Monthly Temperature
25 oC
24th & 27th
Minimum Monthly Temperature
4 oC
16th
Number of Air Frost Days
0
Number of Hot Days (> 25 oC)
2
Monthly Precipitation
26.6 mm
Greatest 24 h Precipitation
7.0 mm
7th - 8th
Number of Dry Days
22
Monthly Sunshine Hours (estimated)
224
Average Wind Speed
3 km/h
Highest Wind Speed
34 km/h
4th
Maximum Barometric Pressure (Sea Level)
1032.8 hPa
26th
Minimum Barometric Pressure (Sea Level)
1007.9 hPa
9th
Average Barometric Pressure (Sea Level)
1022.6 hPa
Heating Degree Days
137.4
Cooling Degree Days
15.5
The monthly profile of daily minimum and maximum temperatures for May 2023 is displayed in Figure 1. Daytime maxima exhibited a small increase as the month progressed whereas the night-time temperatures remained stubbornly low but remained frost-free.
Figure 1: Daily Min/Max Temperatures (May 2023)
The daily rainfall and sunshine (using solar radiation as a proxy) profiles for May 2023 are shown in Figure 2. What relatively little rain fell in May 2023 was confined mostly to an 8-day period (4th to 11th inclusive) in the first half of the month. The second half of May was dry and sunny overall.
Figure 2: Rainfall and Sunshine Data (May 2023)
Compared to previous years (2020 - 2022), May 2023's mean temperature was pretty much in the middle and similar to 2022 (Figure 3). May 2021 was notably colder whereas 2020 was a little higher. The last two Mays (2022 & 2023) have been frost-free which will be welcomed by most gardeners.
Figure 3: Temperature Data for the Last Four Mays (2020 - 2023)
The month of May has experienced a great deal of variability in the amount of rainfall over the past four years (Figure 4). This year it was low though not as low as 2020. While the benefit of less rain is not always more sunshine (see, for example, here), this was the case during May 2020 and 2023. May is often a fairly calm month with relatively low maximum wind speeds - a fact borne out by Figure 4.
Figure 4: Rain, Sunshine & Wind Data for the Last Four Mays (2020-2023)
An overview of the UK weather for May 2023 is provided by the UK Met Office here. The mean temperature anomalies for the UK are displayed in Figure 5 with Herefordshire marked in pen. Most of the UK, including Herefordshire, was around 1 ℃ warmer than average while the South East and East Anglia were only average. The mean Central England Temperature for May was 13.9 ℃ in close agreement with the value (14 ℃) measured by my Davis Weather Station.
Figure 5: UK Mean Temperature Anomalies (Met Office)
UK rainfall in May, as a percentage of the 1991-2020 average, is shown in Figure 6 with Herefordshire highlighted. The 1991-2020 average rainfall for Hereford in May is between 53 - 54 mm based on the nearest Met Office Weather Station at Credenhill, just a couple of miles down the road from us. The monthly precipitation for May recorded by my Davis Weather Station was 26.6 mm (Table 1); i.e. 50% of the typical rainfall for this area in agreement with Figure 6.
Figure 6: Relative Rainfall for May 2023 (Met Office)
Met Office data for sunshine hours (relative to the 1991-2020 mean) in May 2023 are presented below in Figure 7. Typically, May sunshine duration in the UK is between 190 - 200 hours. So the 224 sunshine hours 'recorded' by my weather station (Table 1) would be 115% of the 1991-2020 average - in good agreement with the Met Office data (Figure 7).
Figure 7: Sunshine Hours relative to the 1991-2020 Mean (Met Office)
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