Red Admirals (Vanessa atalanta) overwinter as adults in this area, so occasionally may be seen basking in the sun on mild days in fall or winter. This a medium-sized butterfly, ~5 cm (2 inches) across.
Here's a view from above (next photo). Note the dark brown background with a broad orange stripe in the middle of each forewing. The trailing edge of each hindwing is also orange.
With a slightly closer view, you can see the subtle hints of coppery iridescence and the bright blue accents on the inside corners of the hindwings.
The white spots at the tips of the forewings might remind you of the butterflies known as ladies. Red Admirals are in the same genus, but they're more boldy and simply patterned (at least on the upper surface of the wings). If you'd like to compare, review previous posts on American Ladies, Painted Ladies, and West Coast Ladies.