Based on the weather in Portland, Oregon, United States Of America as of July 31, 2016 2:22am local time

Why? Because it's not very warm out.
Current Conditions
Mostly Cloudy
Temp: 56.3°F13.5°C
Wind: 2.4 MPH3.9 KPH
Precipitation: None

Next 2 hours: Yes

Next 4 hours: Yes

Next 8 hours: Yes