The Relion (Prime?) manual can be found here. The meter is supposed to be able to operate between 5 and 45 deg C and relative humidity of less than 80%. The "e13" error refers to not enough blood on the test strip. The meter itself can be stored between 0 and 50 deg C, but being in a car or direct sunlight may be too much.
The test strips are the most sensitive to temperature and you are advised not to leave the strips above 30 deg C. The strip canisters are airtight, to protect them you can put them in a frio pouch as Ruth suggested. When used properly a frio is claimed to keep it's contents at 18-26 deg C. My experience is that a frio does well in low humidity but can stop working in high humidity.