Here are a couple of recent still life paintings done outdoors working in different qualities of light; overcast, full sun, shade. If you can find great color, you can paint in any light, on any type of day. Light doesn't become flat or dull - the quality of it is always changing throughout the day, but it is never uninteresting.
Red Bowl and Oranges, 12" x 12", Oil on panel, © Eric Merrell
Sunflowers, 16" x 12", Oil on panel, © Eric Merrell
Blues in Sunlight, 12" x 12", Oil on panel, © Eric Merrell