If you're looking for a simple way of improving your fitness levels and burning calories, then the obvious choice is to go for a run or cycle. You don't need a sports club membership nor do you really need any expensive equipment (you can pick up a free bicycle on Freecycle!).
Here are 5 reasons why I recommend that you should run or cycle in the morning especially on a summer's day:
1) At the weekend, there will be less traffic which will mean that there is less chance of you being hit by someone not paying attention; additionally, because there is less traffic, pollution levels will be lower. When you're exercising, you will be sucking in air harder than normal which will mean that if the air isn't clean, you're just breathing toxins deep into your lungs.
2) The air is cooler so you won't sweat so much or overheat. Also, oxygen is denser than when the air is warm so you are effectively breathing more efficiently.
3) There is evidence to suggest that training while in a fasted state can increase fat loss - so consider doing your exercise before eating breakfast. Just remember to bring some water with you.
4) If you train later in the morning, you can eat a lunch without feeling guilty - post-exercise carb loading will feed your muscles and allow them to heal.
5) Most people don't consider exercise their main form of entertainment so if you train in the morning, you can plan to do things for the rest of the day.
Bonus tip: surprise your body with exercise before it's awake enough to know what's going on!