1973 was memorable for the last great September heatwave, a November cold snap, and an exceptional downpour in Kent in September. Overall it was a dry year.
January. Another unexciting month - slightly warmer than average (4.5).
February. Anticyclonic and foggy at first, then with alternating spells of cold and mild weather as winds changed between the mild west and the cold north. There was a severe spell midmonth, with snow and frost, and a minimum of -21C at Carnwath (Lanarks.) on the 15th. On average, a very northwesterly month.
March. Mild, dry, sunny, and anticyclonic. There were some warm days but also some night frosts. There was a particularly warm spell mid-month, with 19C reached in parts of the SE on the 23rd.
April. Cool and unsettled. A stormy first week, with severe gales over England and Wales on the 2nd, and snow in the north. Cold from the 19th with NE winds and snow at times. Eskadalemuir nearly made -10C (-9.9, to be precise) on the 28th-29th.
May. Dull, unsettled, and thundery. There were some warm days midmonth. Very close to the average temperature (11.4) overall. There were some heavy snow showers on the 1st in NE Scotland. There were some heavy thunderstorms in the SE on the 3rd, and again at the end of the month.
June. Very slightly warmer than average (14.8). Quite dry in places.
July. On the cool side. A notable thunderstorm caused disruption in SW London on the afternoon of the 6th: 118 mm of rain fell in two hours, leading to flooding. There was flooding in the Pennines on the 15th as a depression came to a halt. Flooding when waters rose ten feet at Burley (Derbys.). Rush hour traffic took 90 minutes to travel two miles between Bramhall and Cheadle Hulme.
August. Augusts in the 60s and early 70s tended to be rather tame affairs: at 16.5C CET, this was the warmest since 1959. It was also a wet month, and was windy at times in the N and W. The first ten days were unsettled and dominated by westerlies. There was a heavy thunderstorm in the SE on the 1st, with 68 mm of rain in 45 minutes at Balham. 110 mm of rain fell in parts of Wales on the 5th. There was a mini-heatwave midmonth that I remember quite clearly: Southampton was the place to be, with the hottest temperature of the year, 32.1C, on the 14th. A minimum of -4.5C reached at Lagganlia (Grampians) on the 21st; low temperatures in the Highlands were widespread that morning (e.g. -4.4 Grantown-on-Spey, -3.3 Inverdruie). There were some violent thunderstorms in the south on the 27th.
September. Two great things about this month. First, it was a month with a notable heatwave: Gillingham (Kent) reached 31.0C on the 5th. This was the last time 30C was reached in September before 1999 (although 1991 came close) - before this it happened approximately every 16 years. Severe thunderstorms hit Kent on the 15th: e.g. 55 mm of rain in 30 minutes at Herne Bay. Then there was an amazing downpour: 190.7 mm at West Stormouth in Kent in 13 hours on the 20th; this sets the daily rainfall record for the month. At the same time, 172 mm fell in under 19 hours at Margate, starting soon after 5 pm, and 167 mm fell in 13 hours at Ashford. Because of the local nature of thunderstorms, other parts of the country were relatively dry (e.g. there were only 33 mm for the whole month around Oxford). That is just one of the reasons why we love thunderstorms so.
October. A rather cold (9.0C) and generally dry month. The record for the lowest minimum in the first half of the month (-8.5C) was set this year on the 12th, at Lagganlia (Highland). There was an unsettled spell midmonth, with 96mm of rain at Penzance on the 12th.
November. Dry and sunny, yet oddly unsettled at the same time. 147 mm of rain fell at Blaneau Ffestiniog on the 9th. A north wind led to a very cold end to the month, with freezing fog, snow showers, and severe frost. There was a minimum of -15C at Carnwarth (Lanarkshire) on the 29th.
December. A very cold start, but then generally a mild, unsettled month, though with some cold snaps and snow in the north. It was very cold in Scotland on the 1st: after a minimum of -17C early in the morning, in some locations the temperature didn't exceed freezing all day. Christmas Day was notably foggy.