The 14 day weather forecast from the weather network has gotten markedly more reliable over the last few years, so I trust it generally within +/- 5° of what they’re saying.
The “Fall Outlook”, “Winter Outlook” etc that they release are also half decent indicators of the weather trend over the next three months. Can’t set your watch by it of course. Last winter they called for above average temps, which we did experience, but we also got the coldest 3-day period in 80 years during January, so yeah.