Measure the temperature with a thermometer several times a day at the same times each day. Record the measurements.
Measure the air pressure with a barometer at the same times you measure the temperature. Record your readings in inches or millibars.
Look at the sky and record whether the skies are clear, partly cloudy, cloudy or fog.
Look at the wind vane and record from which direction it is blowing. For example, if the wind is blowing from north to south, record that as a north wind. Choose from one of the following directions: north, northwest, northeast, south, southwest and southeast, east and west.
Measure and record the wind speed with an anemometer.
Observe and record the form of precipitation falling. For example, note if it is rain, sleet or snow.
Measure and record the amount of precipitation. If it is raining, use a rain gauge; if snowing, measure depth with a measuring stick. If the snow isn't deep enough to measure, record it as "trace."
Average each of your measurements for each month.
Locate the climatological data for your area on the weatherbase website.
Calculate the difference between your values and those from weatherbase. For example, if the climate data at weatherbase show the normal temperature for June as 82 degrees and your average was calculated to be 80, then the temperature is 2 degrees below normal for that month in the year you monitored the weather.