Long-sleeve sport shirts are perfectly acceptable in summer, so why not long-sleeve rugbys? I'm not talking about the heavy twill variety, the ones used for actual rugby matches. Lightweight cotton jersey works on warm days, as long as you don't over-do it with your under-shirt. Stick to a simple tee, avoid even a polo for layering as extra heat will build, especially around your neck. Next, roll up your sleeves and lastly, never pop your collar unless evading some overbearing sunlight.
Enjoy the visual stoplight of some favorite jersey rugbys.
Happy Independence Day! I'll have an actual July 4th post up in the next day or two.