no its not "safe" temps of 140*F and higher, and temps of -20*F and lower are going to cause problems. Direct sun with a FLat black light , you can imagine the temps that can reach.
But i do it

and have not had a problem yet.
dont Charge in the heat EVER. this would be a HUGE problem.
keep the light somewhere where direct sun and the heat are less, park in the shade, use a mirro reflective type sun shade, on your windshield, crack open the windows a bit.
get roll down reflective shades for side windows (black or tinted are worthless)
get all the Legal windows in the car "tinted" but with mirror reflection type tinting, not black or shaded. legal windows in most states are anything but "A" (driver side) "B" (passenger side) and Windshield. check your local for tint laws.
park in the garage. many things can be done to keep the CAR ITSELF out of conditions that are getting close to or beyond the spec of the battery.
or Just take it OUT of the car, or use an alternative power source when in the car.
remember i said it was NOT safe, the rest is just trying to help.