The Diamond Jubilee celebrations include the sailing of a huge flotilla along the River Thames on Sunday afternoon, with more than 1,000 boats breasting the waves.
The Thames Diamond Jubilee Pageant will pass from Battersea Bridge eastwards to Tower Bridge, hoping for sunshine and sparkling water.
It might be out of luck, though, because MeteoGroup forecasters are expecting grey skies and approaching rain, while a cool breeze comes up the river.
Whatever the weather, it is not going to have much of an effect on the monarch or the monarchy, except perhaps for Her Majesty to protect her hat. On occasion, however, meteorology has had a profound effect on history and the Crown.
Another "flotilla" that we call the Spanish Armada was sent by Philip II of Spain in the summer of 1588 with a view to cutting off English aid to the Dutch rebelling against Spanish rule, and to nipping the Protestant Reformation in the bud.
The outcome is well known and the weather lent a hand that is sometimes overstated but nevertheless significant.
Initially, the invading force of Spanish galleons was able to take advantage of a strengthening south-westerly breeze, with the faster but smaller English vessels hampered by rising waves. But the need to anchor out of formation to take on supplies, ammunition and troops for the planned invasion allowed the English navy to harry them.
It probably did not help, either, that the commander of the Spanish forces, the Duke of Medina Sedonia, was not by any means a sailor and suffered sea-sickness in the stiff winds and heaving seas.
Then in the middle of the night on 28 July Sir Francis Drake ordered fire-ships to be sent on the wind towards the Spanish ships anchored at Calais. Fearing explosion, given the amount of gunpowder on board, the ships' captains slipped anchor and made off in the dark.
The strength of the south-west wind prevented a return to Calais, and the Armada tried to reform off Gravelines where it was again engaged in battle on 8 August and lost 11 ships, either sunk or badly damaged.
Medina Sedonia decided to abandon the invasion and return to Spain to regroup. By now, though, the wind had backed southerly ahead of a fierce storm that is quite likely originally to have been an Atlantic hurricane.
This forced the Spanish fleet to sail north, intending to circumnavigate the British Isles before heading southwards again to Spain. The worsening storm rather famously put paid to that, and became known in England as The Protestant Wind.
Back in 1066, the last time that England was invaded by a belligerent force, the shoe was on the other foot. And this time it was both foul and fine weather that helped dictate the outcome.
The coronation of William the Conqueror in December 1066 might not have happened if it had not been for a stormy English Channel in September preceding a late burst of warmth in October.
William's departure was delayed by unfavourable winds while another claimant to the English throne, Harald Hardrada, King of Norway, sailed across the North Sea. Harold Godwinson force-marched his army northwards to meet the invading force on 25 September at the battle of Stamford Bridge in the East Riding of Yorkshire, where he was victorious.
Meanwhile, the weather had turned to William's advantage in the south, and with Harold's army taking care of business in the north he landed unopposed at Pevensey Bay, East Sussex, on 28 September.
Harold had to speed his soldiers southwards again, and the long, arduous march in the heat of an Indian summer no doubt took its toll. The rest, as they say, is history.
It is conceivable, then, that without the intervention of the weather, England might have seen the return of a Catholic monarch in the 16th century and the repulsion of a Norman duke in the 11th.
Either way, it is possible that the regal procession along the Thames on Sunday might have had a very different monarch at its helm.
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