Icy Cold temperatures & LED lighting get along well together. 

You may not like cold but LED lighting sure does. LED lighting does well in a cold environment. The cold condition allows the LEDs to dump the heat produced while operating. Heat is bad for LEDs. LED lighting works by sending a low voltage DC across a precise gap distance. To jump the gap, plasma forms and is then abruptly halted by the distance the electron travels to the end of the controlled gap. The precise gap distance manufactured in the LED chip allows a specific wavelength of light to be emitted. A larger gap produces a light shifted to the red, and a smaller gap shifts the light further to the violet color spectrum. Heat causes the precise gap spacing in the LED chip to expand and therefore shortens the LED chip's life and disrupts the intended light output color. In addition, if too much heat is retained in the LED chip, the electrical resistance will increase and destroy the chip. As you can appreciate now, the seasonal cold is a welcome benefit for LED-type lighting, so dress warmer if you don't like the cold.

Fluorescent lighting does not perform well with cold temperatures because they rely on mercury becoming vaporized. Every winter season, the cold and the fluorescent lights battle it out. The cold wins every year. The way this type of lighting works depends on heat helping out. First, and most importantly, the mercury within the glass lamp has to vaporize. The mercury will form into a vapor at room temperature and mix with the carrier gas (usually argon). Once enough mercury is vaporized, electricity can easily pass through the vapor, ionizing the atoms. Light is given off by sending high voltage alternating current thru the lamp, causing mercury particles to become ionized within the carrier gas. The light from this now "ionized" mercury vapor is in a wavelength that humans cannot see: ultraviolet. The powdery fluorescent coating on the inside of the glass lamp converts the ultraviolet light into wavelengths we can see as visible light. The heat makes fluorescent lighting work better. Cold causes the light output process needed in fluorescent to break down, flicker, and perform poorly.

I am sure we have all seen this effect on a cold day. The colder it gets, the easier it will be for you to notice which signs are LED illuminated & which ones rely on vaporized mercury.