I know that leds are sensitive to high temperature like all electronic devices. This cause it to overheat, dim, and color shift in case of colored leds. But it is true that led performance decreases also at low temperature like less then 5 degrees celsius?

LED themselves have at cold no issues at all, they would have even higher efficacy, light output and longer life, when operated at cold. But the problem might be with their ballast (supply part): If there are used electrolytic capacitors, these loose their performance (mainly ESR) at low temperature, what might cause ballast malfunction or even damage (depend on it's actual design). And some integrated circuits might shift their parameters so, the ballast would not work properly.

Whay the electrolytic capacitors and some integrated circuits in the LEDs supply unit (Called "Driver" in Israel) loose their performance at low temperature. these devices are also electronic. I think all electronic devices increase perfocmance and life in cold temperature.

@dor123:
Electrolytic capacitors:
These are pretty tricky components. As their name suggest, they do contain an electrolyte (so current carrying liquid), what serve there the purpose of one capacitor's electrode and it's connection to the metallic current collector. Mostly this electrolyte is some kind of salt dissolved in water. And as you know, below some temperature the water freezes. Because a salt is there, this critical temperature is below 0degC. But when approaching this freezing point, the conductivity of the electrolyte drop significantly, causing the resistance of the liquid electrode to rise. This cause the component's filtering capability is compromised, what yield to excessive ripple on the voltage. And due to high pulse currents in ballast circuits, such excessive ripple increase the voltage strain on power components (transistors,...), what might fail as a result way earlier, then the capacitor heat up (the high internal electrolyte resistance cause high power dissipation, what heat the capacitor up, but this take time). Of course, there are ways to ensure such capacitor's poor performance does not overstress any component, but such measures have to be implemented in the ballast design. But when the ballast operation range start from 0degC, there would be features ensuring or proper operation from 0degC or at least safe operation before the ballast heat up. But there would be no features needed for it's safe functionality at e.g. -30degC.

Electronic circuits in general:
You are right for reliability most components for themselves, when operated in ideal conditions. But in the ballast all has to operate together, parameters of one component create operating conditions for the other one (valid even for internal components of an integrated circuit, thus limiting the temperature operating range), etc, and this is other story - all components should maintain their parameters inside some range the rest is designed for.
What it mean "increasing performance"? Increasing output voltage of some internal supply regulator (a hypothetical case)? And what, if such voltage goes above the limit, what some component supplied by this can withstand? I think you might guess the result yourself... :-)

The issue is, then in order for the full circuit to work, not only all component should be functional themselves, but they should be able to operate together. And parameters of each component are somewhat dependent on temperature: e.g. (a bit more realistic case then before) threshold voltage of transistors increase at cold, what e.g. increase the minimum supply voltage some logic circuit need for correct operation.
At the same time, e.g. on the same chip, is a voltage regulator, generating supply for this logic. It's output voltage is thermally compensated in the designed operating temperature range, but outside (colder or hotter then specified) it drop down (typical band-gap reference based behavior). So as a result, below some temperature the logic has not enough supply to work, causing the whole IC to not operate correctly...
These issues are known to the industry, so the required operating temperature range is taken into account for design. But this mean, then the operation of the circuit is guaranteed only inside the specified temperature range. What happen outside, nobody guarantee. It might only deviate in parameters (e.g. suply 70W lamp by only 50W, because voltage reference shift it's value out of it's limits), or even blow up itself (e.g. causing a mains short by keeping both bottom and top halfbridge MOS transistors ON at the same time).