The June sea ice outlook was made available 26 June 2024.
https://www.arcus.org/files/sio/main/June_2024_SIO_Report_Corrected.pdf

The June 2024 median forecasted value for pan-Arctic September sea-ice extent is 4.48 million square kilometers with an interquartile range of 4.21 to 4.74 million square kilometers. The lowest sea-ice extent forecast is 3.1 million square kilometers, which would be a new record low for the satellite period (1979-present), and the highest sea-ice extent forecast is 5.21 million square kilometers.

The aim is to predict:
NSIDC Sea Ice Index extent, compute the total extent (sum of cell areas >15%) for each day and then average the extents from each of the days in the month into a monthly average extent.

The data for past years is at
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/
which at time of claim creation says
year, mo, data-type, region, extent, area

1979, 9, Goddard, N, 7.05, 4.58

1980, 9, Goddard, N, 7.67, 4.87

1981, 9, Goddard, N, 7.14, 4.44

1982, 9, Goddard, N, 7.30, 4.43

1983, 9, Goddard, N, 7.39, 4.70

1984, 9, Goddard, N, 6.81, 4.11

1985, 9, Goddard, N, 6.70, 4.23

1986, 9, Goddard, N, 7.41, 4.72

1987, 9, Goddard, N, 7.28, 5.64

1988, 9, Goddard, N, 7.37, 5.36

1989, 9, Goddard, N, 7.01, 4.86

1990, 9, Goddard, N, 6.14, 4.55

1991, 9, Goddard, N, 6.47, 4.51

1992, 9, Goddard, N, 7.47, 5.43

1993, 9, Goddard, N, 6.40, 4.58

1994, 9, Goddard, N, 7.14, 5.13

1995, 9, Goddard, N, 6.08, 4.43

1996, 9, Goddard, N, 7.58, 5.62

1997, 9, Goddard, N, 6.69, 4.89

1998, 9, Goddard, N, 6.54, 4.30

1999, 9, Goddard, N, 6.12, 4.29

2000, 9, Goddard, N, 6.25, 4.35

2001, 9, Goddard, N, 6.73, 4.59

2002, 9, Goddard, N, 5.83, 4.03

2003, 9, Goddard, N, 6.12, 4.05

2004, 9, Goddard, N, 5.98, 4.39

2005, 9, Goddard, N, 5.50, 4.07

2006, 9, Goddard, N, 5.86, 4.01

2007, 9, Goddard, N, 4.27, 2.82

2008, 9, Goddard, N, 4.69, 3.26

2009, 9, Goddard, N, 5.26, 3.76

2010, 9, Goddard, N, 4.87, 3.34

2011, 9, Goddard, N, 4.56, 3.21

2012, 9, Goddard, N, 3.57, 2.41

2013, 9, Goddard, N, 5.21, 3.78

2014, 9, Goddard, N, 5.22, 3.74

2015, 9, Goddard, N, 4.62, 3.42

2016, 9, Goddard, N, 4.53, 2.91

2017, 9, Goddard, N, 4.82, 3.35

2018, 9, Goddard, N, 4.79, 3.35

2019, 9, Goddard, N, 4.36, 3.17

2020, 9, Goddard, N, 4.00, 2.83

2021, 9, Goddard, N, 4.95, 3.47

2022, 9, Goddard, N, 4.90, 3.47

2023, 9, NRTSI-G, N, 4.37, 2.79