From NOAA’s Global Climate Report – October 2021:
The global surface temperature for October 2021 was 0.89°C (1.60°F) above the 20th century average of 14.0°C (57.2°F) — the fourth highest October temperature in the 142-year record. Only Octobers of 2015, 2018, and 2019 had a warmer October.
For the Northern Hemisphere:
The unusually warm temperatures across much of the Northern Hemisphere land resulted in the warmest October on record for the Northern Hemisphere land, surpassing the previous record set in 2019 by 0.11°C (0.20°F).
And for North America:
According to NCEI’s Regional Analysis, North America had its second warmest October on record with a temperature departure of +2.14°C (+3.85°F). This was only 0.03°C (0.05°F) shy of tying the record set in October 1963. According to Meteorological Service of Canada, Ontario (located in eastern Canada) had October temperatures that were 3.0–6.0°C (5.4°–10.8°F) above average. During October 7–15, several locations across Ontario had maximum temperatures above 20°C (68.0°F).
The time series data is at the top of the page.