Cold temperatures usually cause lamplight swirling or spiraling, when the light appears to swirl or spiral inside the tube. This is even more prevalent when “Energy Saver” lamps are used – these often have higher starting temperatures and will not function correctly in colder applications.
In this case, shield the lamps from the cold draft, from air-conditioning or other sources by using a plastic jacket available from distributors. Make sure the plastic jacket (tube guard) is rated for the lamp/ballast combination. It is not advisable to use tube guards with instant start T8 ballasts as high heat from the lamp ends at end of lamp life may cause the tube guards to melt if the lamps are not changed immediately.
This problem may also be caused by low input voltage or lamp and ballast incompatibility. Check the input voltage, which should be the ballast rated voltage +/-7.5% or change the lamp to a known good lamp. If the condition still exists, change the ballast.