| Year | Mean (DU) | Max. ozone in DU (stations) | Month (maximum) | Min. ozone in DU (stations) | Month (minimum) | % variability |
| 1998 | 258.925 | 276.7 (Kano & Maiduguri) | August | 235.6 (Calabar & PH) | January | 14.85 |
| 1999 | 265.877 | 279.2 (Kano) | June | 242.8 (Kano) | January | 13.04 |
| 2000 | 263.813 | 281.9 (Maiduguri) | May | 242.7 (Calabar & PH) | December | 13.91 |
| 2001 | 263.079 | 281.9 (Kano) | May | 243.1 (Calabar & PH) | January | 13.74 |
| 2002 | 262.462 | 276.8 (Kano) | June | 243.2 (Kano) | January | 12.14 |
| 2003 | 260.079 | 280.4 (Kano) | May/June | 243.0 (PH & Calabar) | January | 13.34 |
| 2004 | 263.476 | 281.1 (Kano) | June | 238.9 (Kano & Maiduguri) | January | 15.01 |
| 2005 | 257.836 | 274.3 (Kano) | May | 240 (Kano) | December | 12.50 |
| 2006 | 262.469 | 280.5 (Kano) | July | 238.3 (Kano & Maiduguri) | January | 15.05 |
| 2007 | 257.954 | 275.0 (Kano) | May | 241.3 (Calabar) | January | 12.26 |
| 2008 | 263.881 | 278.8 (Kano & Maiduguri) | July | 238.3 (Maiduguri) | January | 14.53 |
| 2009 | 259.668 | 276.2 (Kano) | May | 237 (Calabar & PH) | December | 14.19 |
| 2010 | 260.419 | 274.7 (Kano) | July | 237 (Calabar & PH) | January | 13.72 |
| 2011 | 262.249 | 275.1 (Kano) | May | 248.3 (PH) | December | 9.74 |
| 2012 | 260.804 | 283.8 (Kano) | May | 238.5 (Kano & Maiduguri) | December | 15.96 |