25k-marathon race advice

I think you should do the 25K all out since it is a month before your marathon. If you can run a 25K in 1:43, you should be able to run a marathon in about 3:00. Supposedly it takes 1 day to recover per mile raced (so it would take about 2 weeks to recover from either a half marathon or 25 K and 3 weeks to recover from a 20 mile race) Running a 30K or 20 mile race might be more ideal for marathon training than running a 25K, although any of these race distances would be beneficial. I would suggest running in a half marathon race as well, maybe two months before the marathon, aiming to run below 1:25. ( about 6:30 pace).

I think 3 hours is a good possibility. Weather is definitely an important factor in race performance. For example a 3:00 marathon in 60 degree weather is equivalent to 3:05 at 80 degrees according to runworks.com Also how hilly is it? A hilly course may add 10 minutes to your times versus a flat course. Some additional challenges are that this will be your first marathon and it might be very warm. I think if you did a second marathon in the early spring, you will probably run a much better time than you will for your first marathon in the summer heat.

Good luck. Keep us posted!