From the NOAA Global Climate Report – September 2020:
Averaged as a whole, the September 2020 global land and ocean surface temperature was the highest for September in the 141-year record at 0.97°C (1.75°F) above the 20th century average of 15.0°C (59.0°F). This value surpassed the previous record set in 2015 and, again in 2016, by only 0.02°C (0.04°F).
The global land-only surface temperature for September was also the highest on record at 1.47°C (2.65°F) above average. The previous record of 1.40°C (2.52°F) was set in September 2016.
Time series data is available with the link in the box above the climate anomalies map near the top.