Jupiter-Saturn conjunctions happen every 20 years (the last one in 2000.) however this particular conjunction will be especially close – the closest since 1623 and the closest observable since 1226! Don’t worry, if you miss it there is another close conjunction in 2080!
At its closest on 21st December Jupiter and Saturn will be 6 arc minutes apart (1/5 the diameter of the full moon) which is still easily discernable as two separate planets (some reports would have you believe the merge together into an ‘elongated star’)
The weather was poor on the 21st, but there was a gap in the clouds on the 20th, the images from the 20th the planets were at about 9 arc minutes vs 6 arc minutes at closest encounter.