Phew wot a scorcher!  but there there may be trouble ahead........
Steve Head                     July 2018
It won’t have escaped your notice the weather this year has been – unusual.  Here in Oxfordshire people are staggering about like zombies with the realisation that "English summer" – not experienced for years – does still exist and they don't much like it. 
This follows a winter which was a little milder than usual, then the Beast From the East in March and early April brought prolonged cold and high precipitation, much as snow – over most of Britain. The Woodland Trust' Nature's Calendar is still processing data on the response of wildlife to this cold snap, but the evidence is clear that species like bluebells flowered later than usual, butterflies didn’t appear when expected, and immigrant swallows and martins were equally delayed.
When spring grudgingly sprung in mid-April, there was a welcome burst of activity, with lots of plants and insects appearing almost overnight, and we enjoyed a  period of normality.  Then came May, which according to the Met Office was the hottest for 100 years with only about two-thirds of typical rainfall, and June, when the heatwave really set in.  If this continues into August, 2018 will become the hottest summer on record, already averaging 20.9ºC compared with a norm of about 15-16ºC for June and July.
While 1995 was a very dry summer, the outstanding precedent was 1976, with a heatwave averaging 21ºC, and practically no rain anywhere in Britain from June to the end of August (when Denis Howell was appointed Minister for the drought, and severe thunderstorms broke the heatwave within a couple of days).  I will never forget "dancing" naked in celebration with my girlfriend in  midnight lightning and lashing rain, around the garden of my postgraduate hostel in Cambridge. Oh dear, enough of that.
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End of the drought in Cambridge 1976. Figures at the bottom cropped out for reasons of decency.
With only 47mm of rain so far since June 1st, this is already the driest summer since 1961. Even if the weather normalises now, this summer would average one of the top five on record. What can we expect? On Monday 16th July the iNews website reported the heatwave was ending and rain is on its way,  while two days later the Express (never a paper to avoid panic-inducing weather stories) confidently predicted another six weeks of heatwave to come.
What's the effect on the garden?
I’ve noticed exceptional flowering of some garden plants, including the best blossom on my mock-orange for years and quite unparalleled number of flowers simultaneously on my Magnolia grandiflora, which normally puts out one at a time – I count 11 in this image above.
The short lawn grass is burnt to a brown frazzle, although a surprising number of the dicots are still green.  There is an exception – I created my garden pond inside a ghastly huge swimming pool (which was a handy skip when I was renovating the house).  The pond leaks a bit, so the grass above the original pool is kept moist enough to stay green, and its square outline is very clear, even if our dog isn't very interested.
This is a garden-scale cropmark – in dry summers hidden archaeology is clearly revealed by colour changes in faster or slower maturing grass and crops.  There are some remarkable  “garden ghost” cropmarks appearing now – have a look on the BBC website at Clumber Park in Northumberland and Gawthorpe Hall in Lancashire.
The Forum’s excellent Facebook group has had several recent posts with people reporting unusual insects in their gardens.  Lucky Elizabeth Eveleigh, Peter Scott and Rachael Vickers have seen uncommon silver-washed fritillaries Argynnis paphia, one of our biggest butterflies, and normally confined to woodland glades.  In her seminal book “Wildlife of a garden – a thirty-year study”  Jennifer Owen recorded this species once in her Leicester garden – in the summer of 1976.  She considered that the countryside was so baked, with so few nectar bearing flowers available, that this species was a refugee from the drought, nectaring-up in a still-green garden.
What could be the long term effects?
As Tom Bawden pointed out in his inewsletter there are likely to be varied effects for different organisms.  Shallow rooted plants on sparse soils may well die completely, and populations take years to recover. A  field where I walk the dog had even more pyramidal orchids than normal this June, but they finished flowering much quicker than in cooler moister years.  Butterflies this year have enjoyed sunny conditions as adults, and I have seen lots, but again the flight period seems to have ended quickly, perhaps as nectar sources ran out.  Right now, only deep-rooted field scabious is flowering normally in the field, and I’m seeing very few flying insects
The real concern lies with their larvae.  Eggs laid in late May and June will have hatched into a drying world, and brown butterfly caterpillars that feed on grasses will probably face real problems.  We are likely to see a drop in adults next year.  1976 was a clear warning of what to expect.  A recent York University study analysed 50 years of butterfly and moth records, and the most spectacular anomalies in their numbers were between the summers of 1976 and 1977.   In the sun  of 1976, lots of species were recorded flying in large numbers, but in the following summer numbers plummeted, which the authors attributed to starvation in the previous year’s larvae
Variation in populations of Lepidoptera showing effect of 1976 summer. Adapted from Fig 2 of the York paper
It’s likely we will see the same thing again next year, but even worse, because since 1976 average temperatures have climbed higher, and Butterfly Conservation found that wet and gloomy 2017 was the 7th worst butterfly year on record, so we are probably already starting at a low point.
What can you do?
There are no hosepipe bans yet in most areas, so we can legally water the garden and keep vegetation green for caterpillars, and nectar rich flowers blooming for pollinators. While we may be rewarded by seeing rare refugee insects like the silver-washed fritillary, the more important point is that while insects suffer in the countryside, we should be able to keep our garden species going.  This could be an important factor in helping populations everywhere recover next year.  I would recommend letting ponds draw down, try to avoid refilling them with tap water unless in danger of drying to the liner.  Put water out for hedgehogs, bees and birds, but please don’t waste it on the mown lawn, which will green-up again speedily when the weather breaks.
In a wonderful parallel to Denis Howell's instant success as 1976 Minister for drought, just 31 hours after posting this blog, here in Cholsey IT RAINED!  It kept up for three hours of moderate to heavy rain, and the world subsequently feels much relieved.  However, when I look at the soil, all this rain penetrated only about 2.5cm, so the improvement will soon be gone.