First appearance of Kavan Smith as Major Lorne in this series. Smith previously played the character in Stargate SG-1 (1997).
When McKay and Lorne are patrolling after McKay puts on the anti-radiation suit, McKay is complaining about being overheated. Despite this, his exhaled breath is visible, indicating the air temperature is cold. Hazmat suits do not allow a whole lot of airflow (which is filtered). You can easily overheat even in chilly conditions, especially if you are doing physical activity.