Based on the weather in Salisbury, Wiltshire, United Kingdom as of September 1, 2015 11:15pm local time

Why? Because it's not very warm out.
Current Conditions
Temp: 55.4°F • 13°C
Wind: 7.4 MPH • 11.91 KPH
Precip: 0%

Next 2 hours: Yes

Next 4 hours: Yes

Next 8 hours: Yes