July 20 in Boston
Weather forecasts run out after about two weeks. For any date further out than that, the honest answer isn't a single number — it's the range Boston actually delivers on this date, and how often.
On July 20, Boston, MA typically reaches 84°F, but has run anywhere from 72°F to 93°F in eight years out of ten. About 69% of July 20s see no measurable precipitation.
The odds on July 20
Odds computed from the last 30 years (1997–2026).
We scored real forecasts against the station at BOSTON. A next-day forecast there misses the high by 2.7°F on average; by 7 days out that grows to 6.1°F. The range on this page spans 21°F, so inside about two weeks a real forecast is far sharper — past that, there isn't one, and this is what's left. See how your city ranks.
Where this comes from: 852 daily observations from BOSTON, covering 1970–2026. We pool every day within 7 days of July 20 — a single calendar date has only about 56 readings, far too few to place a 10th percentile you'd want to trust.
Why it's not a plain average: A climatology computed straight across 1970–2026 describes the middle of that period, not today, so as a statement about the present it runs cold. We fit a trend on year and shift each observation to 2026 before taking the range. The probabilities use the last 30 years instead — shifting a temperature along a trend is well defined, shifting “did it rain” is not.
What this is not: Not a forecast. It is what Boston, MA has actually done on this date, which is the only defensible answer once you're past the two-week horizon where real forecasts stop. Data: NOAA NCEI GHCN-Daily.