It is 200 years ago this month that London enjoyed its last frost fair.

Weeks of hard frost from the day after Boxing Day was enough to freeze the river between the old London Bridge and Blackfriars, enabling dozens of opportunist London traders to set up stalls and booths selling souvenirs, drinks and food.

Unlicensed gambling, drinking and dancing was the order of the day for those brave enough to venture on to the ice. A sheep was roasted on the ice with the public charged to look at it, and charged again for a slice of “Lapland mutton”. At one point an elephant was led across the ice at Blackfriars.

The ice was however, not very stable. Boatmen deprived of an income charged visitors a penny to cross planks to get on to the ice. They were on hand to rescue two women who fell through, although a plumber carrying lead was not so lucky.

Though changes to the flow of the Thames has vastly reduced any chance of a frost fair being repeated I’ve often wondered what the day to day climate would have to be like to freeze the Thames as it did in 1814.

Luke Howard’s Climate of London provided a starting point. His pioneering measurements of the atmosphere taken outside his laboratory by the River Lea in Stratford, though not as accurate as today’s readings, provide an excellent insight into just how cold the season was.

I was surprised to find that the stats compare well with the winter of 1962/63 – the coldest winter in recent memory. Obviously Howard’s readings would not have been as accurate as today’s – his thermometers were initially suspended in a laurel bush to shield solar radiation – but they would still have been close.

I have converted his readings  in Fahrenheit to Celsius and plotted them on a spreadsheet here. As well as records of temperature, wind, rain and moon phase Howard also included any notable weather events in his diaries from both home and abroad.

The winter of 1813/14 started mild. On December 16th he noted that “bees quit the hive in unusual numbers for the season”. During the following days up to Christmas Day wind and rain alternated with misty, occasionally frosty, mornings – probably not unlike some of the weather we experienced last month.

However, Boxing Day brought a big change: “Since the 26th we have had a succession of thick fogs with a calm air or at most a breeze from the NE. Yesterday the air cleared a little and today has been fine; a display of cirrus clouds with much red in the morning and evening sky,  the peculiar smell of electricity has been perceptible of late when the air cleared up at sunset.” Howard goes on to report that there was an eruption of Mt Vesuvius in Italy.

The beginning of January saw the mists thicken into heavy freezing fogs: “The mists which have again prevailed for several days and which have rendered travelling dangerous.”

In those days, with cloud identification in its infancy, Howard identified the fog as stratus and noted with wonder the formation of rime frost on everyday objects: “The air has been in effect loaded with particles of freezing water such as in a higher region would have produced snow.  These attached themselves to all objects crystallizing in the most regular and beautiful manner. A blade of grass was thus converted into a pretty thick stalagmite some of the shrubs covered with spreading tufts of crystals looked as if they were in blossom while others more firmly incrusted might have passed for gigantic specimens of white coral.”

By January 5th  a “deep snow brought by an easterly wind had reduced the whole scenery to the more ordinary appearances of our winter”.  More snow followed on the 6th and piled into drifts on a strengthening NE’ly. The biting gusts presented Howard with yet another new winter phenomenon: snow rollers:  “With the temperature at the surface 33 or 34F presented an amusing phenomenon which was pointed out by my children. Instead of driving loose before the wind it was collected occasionally into a ball which rolled on, increasing till its weight stopped it. Thousands of these were to be seen lying in the fields some of them several inches in diameter”.

On the 9th Howard describes a misty morning and a snowy landscape that had a “bluish tint”. The “blueness” of the air is possibly down to the sheer cold – it was -13.3C that morning. I’ve seen something similar, a bluish hue to the air, on very cold mornings in the Alps. Howard notes that the minimum on the surface of the snow that night, the coldest of that winter, was -14.4C.

On the 11th a “very red” sunrise was observed . By the 12th Howard describes the Arctic scene from his laboratory: “The River Lea is now firmly frozen and the Thames so much encumbered with ice that navigation is scarcely practicable.” Howard also notes on this date that the snow in upper parts of Hampshire and “on the Hind Head” had fallen to a depth of 15 feet in places.

A slight thaw was noted on the 16th from the warmth of the earth. More snow fell on the 18th and 19th. Snow on the 20th was accompanied by a strong NE’ly. On the morning of the 21st Howard noted drifts “many feet deep”.

The 22nd to the 25th saw more outbreaks of snow before the wind swung into the SW on the 26th with snow followed by rain – the cold spell was beginning to lose its grip. Howard notes on the 29th: As the barometer began to rise the wind came round by SW to NW and blew with great violence till near morning”. Classic freeze/thaw conditions followed over the next few days before the real thaw, and the end of the frost fair, arrived on February 5th. Howard notes: “Crimson sky at sunrise hollow wind snow and sleet. 6th A gale from SW with showers of rain at evening.”

The rest of February, and meteorological winter, appears fairly nondescript. Howard notes that on the 12th a gunpowder explosion resulting in a fire at the Custom House, 5 miles south, caused a  “shower of fragments of burnt paper”. Sharp frosts and misty mornings prevailed to end of month, Howard noting the “clear orange twilights”, probably caused by the eruptions in Italy that formed a new crater on Vesuvius. Howard mentions a letter he received from Heligoland on February 21 which had also seen intense frost that was preceded by thick fogs and heavy falls of snow. The latter was 10 and 12 feet deep – the frost lasting six weeks.

Howard wrote his own account of the frost fair…

“The Thames Frozen Over

January 15: The masses of ice and snow had accumulated in such quantities at London Bridge on the upper side yesterday that it was utterly impossible for barges or boats to pass up. During the whole of this week that part of the Thames below Windsor Bridge called Mill River has been frozen over and has been crowded with persons skaiting.

February 3: The confidence of the public in the safety of the passage over the frozen surface of the Thames was yesterday increased. All the avenues from Cheapside to the different stairs on the banks of the river were distinguished by large chalked boards announcing A safe footway over the River to Bankside and in consequence thousands of individuals were induced to go and witness so novel a spectacle and many hundreds had what we cannot help terming the fool hardiness to venture on the fragile plain and walk not alone over but from London to Blackfriars Bridge. Several booths formed of blankets and sail cloths and ornamented with streamers and various signs were also erected in the very centre of the river where the visitors could be accommodated with various luxuries. In one of the booths the entertaining spectacle of a sheep roasting was exhibited

February 7: Friday several printers brought presses and pulled off various impressions which they sold for a trifle eg Printed to commemorate a remarkably severe frost which commenced December 27, 1813, accompanied by an unusual thick fog that continued eight days and was succeeded by a tremendous fall of snow which prevented all communication with the Northern and Western Roads for several days. The Thames presented a complete field of ice between London and Blackfriars Bridges on Monday the 31st of January, 1814. A Fair is this day February 4, 1814, held and the whole space between the two Bridges covered with spectators. This field of ice was indeed a very rugged one consisting of 1 masses of drift ice of all shapes and sizes covered with snow and cemented together by the freezing of the intermediate surface. The deceitfulness of the latter caused as is too common on such occasions the loss of some lives by drowning. The following passage announcing the opening of the river soon after is worthy of preservation on account of the spirit in which it is written.

February 11: We are happy to see the lately perturbed bosom of Father Thames resume its former serenity. The busy oar is now plied with its wonted alacrity and the sons of Commerce are pursuing their avocations with redoubled energy. Cheerfulness is seated on the brow of the industrious labourer those who were reduced to receive alms as paupers again taste the sweets of that comparative independence with which labour crowns the efforts of the industrious. What a fruitful source of congratulation does this prospect afford nor can the contemplative mind dwell on the subject without feeling gratitude to that beneficent Being who in a time of such calamity opened the hearts of the benevolent to administer from their abundance to the necessities of their poorer brethren and thus add cement to the bond by which all mankind are linked together. The mischief done on the river during the late frost is greater than can be remembered by the oldest man living. Among the craft alone it is calculated to amount to upwards of 10,000 independent of the damage sustained by the cables tackle & of the shipping.”