The dates that matter
If you want to run a major fall 2026 marathon, the time to plan is now — not in August. Key dates:
Berlin: September 27 (16 weeks out) Chicago: October 11 (18 weeks out) Amsterdam: October 18 (19 weeks out) Frankfurt: October 25 (20 weeks out) New York: November 1 (21 weeks out)
A 16-week plan is the minimum for someone with an existing solid base. If you need to build that base first (currently under 35-40 km/week), add a month of foundation work first.
Assess your current base honestly
Before starting a marathon plan, three honest questions:
How many kilometers per week? A minimum of 40-50 km/week for 4+ consecutive weeks is recommended before starting a 16-week plan. Below that, injury risk climbs significantly in weeks 8-12 when training volume peaks.
What's your long run status? If you haven't done a 25-28 km run since spring, your June training should include one soon — at very easy pace (zone 2, conversational).
Any persistent aches? Tendinopathies (Achilles, IT band, plantar fascia) worsen under increasing load. If something's pulling, June is the time to address it — not ignore it.
The unexpected advantage of summer training
Summer training has a bad reputation among runners. But heat adaptation produces documented physiological benefits that actually improve performance in cool conditions.
Running in heat for 2-4 weeks triggers plasma volume expansion — the fluid that carries red blood cells. This increased plasma volume improves cardiac output at equivalent effort, and it persists several weeks after returning to cool temperatures. Your Berlin marathon in September will directly benefit from the hot July runs you're doing now.
The 10% rule and your target progression
The universal safety guideline in marathon training: don't increase weekly volume more than 10% per week. If you're running 40 km this week, next week targets 44 km max — not 50.
Realistic progression for Berlin (16 weeks from 40 km/week): June (weeks 1-4): 40-50 km/week, long run 22-25 km Sunday July (weeks 5-8): 50-65 km/week, long run 25-30 km August (weeks 9-12): 65-80 km/week, first 35 km long run September (weeks 13-16): progressive taper, race day