This plan is compressed
The standard Couch to 5K takes nine weeks. This one fits in under four, so the ramp is steeper. The realistic goal is to finish 3.1 miles mixing running and walking, and run most of it if the build goes well. Plenty of people walk turkey trots.
If a session feels too hard
Repeat it instead of moving on, or swap in the previous session. Skipping a day costs nothing; adding extra running to catch up is how shins and knees get hurt. Easy pace: you can speak in short sentences.
Cold-weather basics
Dress for about 15 °F warmer than the thermometer says. Wear layers you can tie around your waist, a hat and gloves, and shoes with some grip for wet leaves. Walk the warm-up even if you feel fine.
Race day
Run/walk from the start: try 9 minutes running, 1 minute walking, or walk through every water stop. Start slower than feels necessary. Eat something light 2 hours before and don't try new shoes or gear.
Not medical advice. If you've been inactive for a long time, have a health condition, or feel chest pain, dizziness, or sharp pain while exercising, check with a doctor first.