Syntax error needs fresh eyeballs

My schema includes three tables and psql throws an error I'm not seeing
when I try to read the schema into the database. I'd appreciate fresh eyes
looking at the table and learning what error I'm not seeing.

The tables:

CREATE TABLE Weather (
site_id INTEGER PRIMARY KEY,
site_name TEXT,
site_location TEXT
);

CREATE TABLE Weather_Params (
site_id INTEGER
REFERENCES Weather(site_id),
param TEXT,
param_unit TEXT,
freq INTEGER,
freq_unit TEXT,
equip TEXT,
PRIMARY KEY (site_id, param)
);

CREATE TABLE Weather_Data (
site_id INTEGER
REFERENCES Weather(site_id),
monit_date DATE,
monit_time TIME,
read_by TEXT, -- name of employee collecting data
param TEXT
REFERENCES Weather_Params(param),
param_value REAL,
PRIMARY KEY (site_id, monit_date, monit_time, param)
);

The error:

ERROR: there is no unique constraint matching given keys for referenced
table "weather_params".

TIA,

Rich