A method of operating an optical icing conditions sensor for an aircraft, the method comprising: transmitting, with a first transmitter, a first light beam having a first wavelength through an optical window of the aircraft at a first transmitting angle relative to the optical window, wherein the first light beam illuminates a first illumination volume; transmitting, with a second transmitter, a second light beam having a second wavelength through the optical window of the aircraft at a second transmitting angle, wherein the second light beam illuminates a second illumination volume; receiving, with a first receiver, light at a first receiving angle relative to the optical window, wherein the first receiver is configured to receive light having the first wavelength over a first receiver field of view, wherein the first receiver field of view overlaps with the first illumination volume at a first predetermined distance; receiving, with a second receiver, light at a second receiving angle, wherein the second receiver is configured to receive light having the second wavelength over a second receiver field of view, wherein the second receiver field of view overlaps with the second illumination volume at a second predetermined distance; measuring, with a controller, a first intensity of light received by the first receiver; measuring, with the controller, a second intensity of light received by the second receiver; characterized by comparing, with the controller, the first intensity to a first threshold value; comparing, with the controller, the second intensity to a second threshold value; determining, with the controller, that a cloud is present if either the first intensity is greater than the first threshold value or the second intensity is greater than the second threshold value; calculating, with the controller, a ratio of the first intensity to the second intensity if the controller determines that a cloud is present; and determining, with the controller, using the ratio of the first intensity to the second intensity, whether the cloud contains liquid water droplets, ice crystals, or a mixture of liquid water droplets and ice crystals; wherein a first reflecting angle is defined by the first light beam transmitted at the first transmitting angle and light received by the first receiver at the first receiving angle, a second reflecting angle is defined by the second light beam transmitted at the second transmitting angle and light received by the second receiver at the second receiving angle, the first light beam has a first scattering intensity at the first reflecting angle, and the second light beam has a second scattering intensity at the second reflecting angle. transmitting, with a first transmitter, a first light beam having a first wavelength through an optical window of the aircraft at a first transmitting angle relative to the optical window, wherein the first light beam illuminates a first illumination volume; transmitting, with a second transmitter, a second light beam having a second wavelength through the optical window of the aircraft at a second transmitting angle, wherein the second light beam illuminates a second illumination volume; receiving, with a first receiver, light at a first receiving angle relative to the optical window, wherein the first receiver is configured to receive light having the first wavelength over a first receiver field of view, wherein the first receiver field of view overlaps with the first illumination volume at a first predetermined distance; receiving, with a second receiver, light at a second receiving angle, wherein the second receiver is configured to receive light having the second wavelength over a second receiver field of view, wherein the second receiver field of view overlaps with the second illumination volume at a second predetermined distance; measuring, with a controller, a first intensity of light received by the first receiver; measuring, with the controller, a second intensity of light received by the second receiver; comparing, with the controller, the first intensity to a first threshold value; comparing, with the controller, the second intensity to a second threshold value; determining, with the controller, that a cloud is present if either the first intensity is greater than the first threshold value or the second intensity is greater than the second threshold value; calculating, with the controller, a ratio of the first intensity to the second intensity if the controller determines that a cloud is present; and determining, with the controller, using the ratio of the first intensity to the second intensity, whether the cloud contains liquid water droplets, ice crystals, or a mixture of liquid water droplets and ice crystals; wherein a first reflecting angle is defined by the first light beam transmitted at the first transmitting angle and light received by the first receiver at the first receiving angle, a second reflecting angle is defined by the second light beam transmitted at the second transmitting angle and light received by the second receiver at the second receiving angle, the first light beam has a first scattering intensity at the first reflecting angle, and the second light beam has a second scattering intensity at the second reflecting angle.