Measurement of the pH of Rain

Today, with precipitation in the forecast, I set up my mini-laboratory to measure the pH of the local rainfall in Stormstown, PA. First, I installed a standard rain gauge to collect rainwater.

pH-1

I calibrated my pH meter, prior to taking any actual measurements, using standard reagents of pH of 4.0 and 6.86. I used a pH 7.0 reagent to verify.

pH-2

After calibration, I waited for some rainfall and then collected my sample.

P1030560

It had rained 0.20 inches over the past two days.

P1030561

This was about 400 ml of liquid.

P1030564

I measured the pH to be about 5.15, which is in the normal range for rainfall but still acidic. It is not considered to be acid rain.

pH Scale

Halfmoon Valley Rainfall

After the rainfall from yesterday and early this morning (1.10 inches), the annual precipitation is now at a surplus of 0.17 inches. Monthly precipitation has been below normal for January, February, March and April. May is not quite over, but the rainfall for the month is 1.74 inches above normal.
Outlook
The outlook for the summer months of June, July and August indicates equal chances for a near normal amount of precipitation.