Now that reminds me of the time I rode through Glen Coe one November morning and my dash was telling me it was -5c. We saw a lovely frozen waterfall but I wasn't about to remove my gloves to take a photo !!
Love my family almost as much as my 90th anniversary RT
If there is that level of ice on the Screen I would be looking more to the road surface before attempting to set off riding. Year before last (Late September) I stayed overnight at a Hotel right next to Le Puy en Velay / Loudes Airport which is 2800 ft above sea level. Next morning the RT was well and truly iced over. I walked down to the main road to find there was clear evidence of black ice. I hung around till mid morning when the sun had melted the ice and I was on my way, albeit cautiously. Incidently, the road in question is the N102 which a cracker, especially the stretch which runs down the Ardeche valley to Aubenas.