CLIMATE & HYDROLOGICAL ANALYSIS

Standardized Precipitation Index

Calculate SPI for multiple accumulation timescales directly in your browser. Your precipitation data remains on your computer and is never uploaded.

Precipitation Dataset

Upload a CSV containing monthly precipitation.

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Drop your CSV file here

or select a file from your computer

Browse CSV

Required columns: Date and Precipitation

CSV

SPI Timescales

Select the timescales to calculate.

SPI-1 1 month SPI-3 3 months SPI-6 6 months SPI-9 9 months SPI-12 12 months SPI-24 24 months SPI-48 48 months

SPI Method

Calculation workflow used by the application.

Monthly precipitation

Monthly precipitation values are read from the uploaded CSV.

Accumulation

Precipitation is accumulated over the selected SPI timescale.

Gamma distribution

Positive accumulated precipitation is fitted using a Gamma distribution.

Zero probability

The probability of zero precipitation is incorporated into the distribution.

Normal transformation

The cumulative probability is transformed to a standard normal variate.

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Your data stays local

The CSV is processed entirely inside your browser. No server or API is used.

SPI Results

Calculated Standardized Precipitation Index values.

SPI Time Series

Result Data

Preview showing the first 100 records.

SPI Classification

Standard interpretation of SPI values.

≤ -2.00 Extremely dry

-1.99 to -1.50 Severely dry

-1.49 to -1.00 Moderately dry

-0.99 to 0.99 Near normal

1.00 to 1.49 Moderately wet

1.50 to 1.99 Very wet

≥ 2.00 Extremely wet