# How accurate is FloodRoute?

We predict how high every tide that could flood will get, a day ahead, then check it against NOAA's real measurement. Misses included.

A day ahead, FloodRoute typically lands within 2 inches of the real water. Tide tables: 5.5.

- **Past 12 months (1533 high tides):** FloodRoute was usually off by 2 inches, tide tables by 5.5. FloodRoute was within 3 inches 68% of the time, tide tables 26%.
- **Past 30 days (255 high tides):** FloodRoute was usually off by 2.5 inches, tide tables by 7.5. FloodRoute was within 3 inches 57% of the time, tide tables 14%.

## Results by location

- **San Francisco:** usually off by 1.4 in. Within 3 inches 85% of the time, tide tables 21%.
- **Virginia Key:** usually off by 1.4 in. Within 3 inches 81% of the time, tide tables 26%.
- **South Port Everglades:** usually off by 1.5 in. Within 3 inches 81% of the time, tide tables 35%.
- **St. Petersburg:** usually off by 1.8 in. Within 3 inches 70% of the time, tide tables 15%.
- **Charleston:** usually off by 2.4 in. Within 3 inches 62% of the time, tide tables 31%.
- **Boston:** usually off by 2.6 in. Within 3 inches 55% of the time, tide tables 17%.
- **The Battery:** usually off by 2.6 in. Within 3 inches 55% of the time, tide tables 37%.
- **Sewells Point:** usually off by 3.1 in. Within 3 inches 49% of the time, tide tables 17%.

## Predictions improve as the tide gets closer

- 24 hours before: within 3 inches 68% of the time
- 12 hours before: within 3 inches 78% of the time
- 3 hours before: within 3 inches 89% of the time

## How we check it

Our prediction is NOAA's tide table plus how far the water is running above or below it, using only readings from at least 24 hours before the tide. The real water is the highest reading at the NOAA gauge within an hour of the tide. "Usually off by" is the middle result: half of the predictions were closer, and half were further off. On average our predictions run 0.3 inches low. A result marked Locked was saved before the tide and can never change; the rest were worked out afterwards from what was known a day ahead. This is the water height at the NOAA gauge, not whether your street flooded.

Live page: https://floodroute.com/accuracy