Rainfall Tracker

Keep a simple rain gauge log. Enter each day’s reading, and the tracker adds up monthly and year-to-date totals, counts rainy days, compares totals with the normal rainfall you enter for your area, and draws a monthly chart. Your log is kept in this browser and can be exported to CSV at any time.

How to use the rainfall tracker

1. Read your rain gauge at the same time each day — many observers read at 7 a.m. and record the rain for the previous 24 hours.
2. Enter the date and amount, then click “Add / update reading”. Entering a date again replaces that day’s reading.
3. Optionally enter the normal monthly rainfall for your area to compare.
4. Check the monthly table and chart; export a CSV to back up or to open in a spreadsheet.

Readings are stored in inches internally and shown in inches or millimetres. Switching units converts everything instantly.

Reading a rain gauge correctly

• Place the gauge in an open spot, away from trees and buildings — a common guideline is a distance at least twice the height of the nearest obstruction.
• Mount it level, with the top about 2–5 feet above the ground, clear of splash.
• Read at eye level at the bottom of the curved water surface (the meniscus).
• Empty the gauge after each reading.
• For snow, melt the contents of the gauge and record the water equivalent.
• Record “trace” (T) for amounts too small to measure; the tracker treats it as zero.

Understanding rainfall totals

Weather services publish climate normals for official stations; in the United States these come from NOAA’s National Centers for Environmental Information, and other countries’ meteorological services publish similar averages. Rainfall varies a lot over short distances, especially in thunderstorms, so your gauge can differ from a station a few miles away.

Why keep a rainfall record

• Gardening — most gardens need about an inch (25 mm) of water a week in the growing season; your log tells you how much to irrigate.
• Lawn watering — avoid watering after good rain and save water.
• Farming and orchards — plan planting, spraying and harvest.
• Rainwater harvesting — estimate how much a roof can collect.
• Drainage and flooding — record heavy events and see which amounts cause problems.
• Citizen science — volunteer networks collect daily precipitation reports from backyard observers and use them for weather and climate monitoring.

Worked example

In April, a gardener records 0.25 in on the 3rd, 1.10 in on the 9th, 0.40 in on the 15th and 0.62 in on the 22nd. The tracker totals 2.37 inches on 4 rain days, with the wettest day on the 9th. The gardener enters 3.40 inches as the normal April rainfall for their area, so April finished 1.03 inches below normal — about 70% of normal — which explains why the vegetable beds needed extra watering.

Rainwater harvesting estimate

One inch of rain falling on 1,000 square feet of roof yields about 623 US gallons (1 mm on 1 m² gives 1 litre). Multiply your roof’s footprint by the rainfall and by a collection efficiency of around 75–90% to allow for evaporation, splash and first-flush diverters. Your monthly totals from the tracker show when your tank will fill and when it is likely to run dry.

Choosing a rain gauge

Keeping a consistent record

Consistency matters more than precision for a personal rain record. Read the gauge at the same time every day, even if it has not rained, and record zero rather than leaving the day blank, so you can tell a dry day from a missed reading. If you are away, note the dates and record the accumulated total when you return as a multi-day reading. Check the gauge for leaves, insects and bird droppings, and clean it every few weeks. Over a few years, your own records become a valuable local climate history for your garden or farm.

Your data and privacy

The tracker saves readings in your browser’s local storage on this device. Nothing is sent to a server. If you clear browser data or switch devices, the readings will not be there, so export a CSV regularly. You can import the CSV again later to restore the log.