Started riveting the rear spar together this morning. Up at 5:15am and it was 1 degree outside. Fired up the heaters and it was bearable out in the garage. Cleco'd the large doublers that attach to the rear spar at the root end and squeezed in a few rivets. Good to be back at the airplane again. I took most of the week off due to the extreme, single digit, cold temps.