It's normal for your body to retain excess water during pregnancy. This can be on average 2 to 3 liters. In the last month, especially, this is very noticeable; symptoms include swollen hands, feet and face. Even in warm weather, you will retain water and may find swelling in your ankles.
Water retention has nothing to do with the temperature. It's important to drink a lot - your body is better able to remove the extra water when you drink enough. Retention of fluid can be benign as long as your blood pressure remains normal, but edema could be a sign of increased blood pressure.
Tips to help prevent edema:
Drink a lot of water. A pillow under your feet or under the foot end of the mattress also helps. This promotes the return of moisture to the cells. This helps you function better. What women sometimes use to prevent edema are diuretics; consult your doctor before doing this!
Contact the obstetrician or gynecologist if you suddenly feel like you're holding a lot of fluid. It can be a sign that your blood pressure has increased, especially if it comes in conjunction with nausea or headaches.