Short answers, pulled from the story.
The Last Glacial Maximum occurred between approximately 26,000 and 20,000 years ago. Researcher Jennifer French dates its onset at 27,500 years ago, with ice sheets at their maximum around 26,000 years ago and deglaciation commencing between 20,000 and 19,000 years ago. In Britain it is known as the Dimlington Stadial, dated between 31,000 and 16,000 years ago.
The average global temperature about 21,000 years ago was roughly 6 degrees Celsius colder than today. Low-to-mid latitude land surfaces at low elevation cooled on average by about 5.8 degrees Celsius relative to present-day temperatures, based on analysis of noble gases dissolved in groundwater.
Sea level was about 125 meters lower than at present during the Last Glacial Maximum, according to the United States Geological Survey. That drop exposed continental shelves, joined landmasses, and created extensive coastal plains across the globe.
Forests shrank dramatically and most of the world's deserts expanded. The Amazon rainforest was split into two large blocks by extensive savanna, and in extreme cases such as Southern Australia and the Sahel, rainfall may have been reduced by as much as 90 percent. Only in Central America and the Choco region of Colombia did tropical rainforests remain substantially intact.
Europe experienced a human population decline estimated at up to 60 percent. In North America, glaciers pushed early human populations into refugia, which reshaped their genetic variation through mutation and drift, establishing the older haplogroups found among Native Americans today.
The Laurentide Ice Sheet covered essentially all of Canada east of the Rocky Mountains and extended south roughly to the Missouri and Ohio Rivers, reaching eastward to Manhattan. At its peak it stood about 3.2 kilometers high around Keewatin Dome, with a total maximum volume estimated at 26.5 to 37 million cubic kilometers.