Points to Remember. 1  Marijuana refers to the dried leaves, flowers, stems, and seeds from the hemp plant, Cannabis sativa. 2  The plant contains the mind-altering chemical delta-9-tetrahydrocannabinol (THC) and other related compounds. 3  People use marijuana by smoking, eating, drinking, and inhaling it.
A cold front is symbolized on a weather map as a line with triangles. The triangles can be thought of as icicles. Cold fronts are often coloured blue. The presence of a cold front means that cold air is advancing and pushing underneath warmer air.
polar air masses bring clear, cold, dry air to much of North America. In summer, the air mass is milder. Storms may occur when continental polar air masses move south and collide with maritime tropical air masses moving north. How Air Masses Move When an air mass moves into an area and interacts with other air masses, it causes the weather to change.