Yes it is possible but they should not spend a night outside until it is at least 15 °C. You need to adjust them slowly to living outside. When it gets to 15°C during the day put them out in a run (but not on grass as the ground won't be dry enough) and bring them in when the temperature goes below 15°C. This helps to acclimatise them. Give them plenty of things to hide in with 2 exits and make sure you cover the run with an old blanket. Don't be surprised if the run for cover at the slightest noise or hide away for the first few days or so as this is a new and scary environment for them. They will soon get used to it.
When the nights start to draw in in August (if you are in the UK) this is when piggies start to grow their nice thick undercoat to help keep them warm in the colder months. (You will find they moult ALOT) If you wish to leave them outside for winter, it is best that they go in a shed or garage (No car in garage) have an insulating cover and a thermal waterproof cover on the hutch, fleece hideys, fleece snuggle tubes, snugglesafes and LOTS AND LOTS of hay.