Map from Google - South_Georgia

In South Georgia, an island of the southern Atlantic Ocean administered by the United Kingdom, the climate is maritime subpolar, so that the average temperature of the warmest month, February, is just 43 °F in the main city, Grytviken.
Winter is cold, and the daily average of the coldest months is around freezing.
Here are the average temperatures of Grytviken.
Average temperatures - Grytviken
Min (°F)373937343028282830323436
Max (°F)464846433936363739414345

The island is exposed to the intense and incessant flow of the westerly winds, related to disturbances, which bring rain or snow throughout the year. The annual precipitation amounts to 55 inches per year in Grytviken, and is well distributed throughout the year, although it drops slightly below 4 inches per month from September to January, that is, between spring and early summer, while it hovers between 4.5 and 5.7 inches per month between February and August, that is, from late summer to late winter.
Here is the average precipitation.
Average precipitation - Grytviken
Prec. (in)

Given the temperatures, snowfall is more likely from mid-April to October, but sometimes it can occur even in summer, even at sea level. Gale force winds may blow throughout the year, the humidity is consistently high, and the amount of sunshine scarce.
At sea level, the temperature can drop a few degrees below freezing even in summer, while in winter it can drop to 10/14 °F after the outbreaks of Antarctic air masses, although the severe frost doesn't last long, because soon the westerlies start to blow again. On the other hand, practically in South Georgia it never gets hot: the temperature can reach at most 68/72 °F, from November to March.
In inland areas, where there are hills and mountains, the temperature decreases, and given the low summer temperatures, glaciers cover most of the island already at 1,000 feet above sea level, and some glacier tongues descend by gravity to the sea. The more you go up in altitude, the easier it is to see the snow fall even in summer. The highest peak is Mount Paget, 9,629 feet high.

South Georgia

The sea is very cold throughout the year, and in winter approaches freezing, although the sea, being salty, freezes at about 28 °F.
Sea temperature - Grytviken
Sea (°F)373737373634343232323436

When to go

The best time to visit South Georgia is the austral summer, from December to March, and especially from January to March, when the temperatures are higher. It must be said that in this period the weather is not always clement: the temperature is low, it can rain, the wind often blows, and in inland hills and mountains (but sometimes even on the coast), it can snow. It will therefore be useful to bring warm clothes, hoping to have the chance to remove some of them in warmer days, when the temperature can approach 68 °F.

What to pack

In winter (June to August): warm clothes, fleece, down jacket, wind jacket, warm hat, gloves, scarf, raincoat, hiking boots.
In summer (December to March): warm clothes, sweater, raincoat, down jacket, hat, hiking boots; the outwer layer can be removed in the warmer days. For the inland hills and Mount Paget, warm clothes like in winter.