Why does my well pump keep losing pressure after it rains?

The rain correlation is actually a useful clue — it narrows this down to a couple of likely causes.

Most likely: waterlogged pressure tank. If the bladder or diaphragm inside your pressure tank has failed, the tank fills with water and loses its air cushion. What happens then is the pump cycles on and off rapidly (short-cycling), and after heavy rain when the water table is high and there's more load on the system, you'll notice the pressure drop more noticeably. You can do a quick test: turn off power to the pump, open a faucet to bleed pressure down to zero, then tap on the tank. If it sounds solid (like tapping a full water bottle) instead of hollow near the top, the bladder is likely shot. Also check the Schrader valve on the tank — if water comes out instead of air, that confirms it.

Second possibility: surface water infiltration. After heavy rains, surface runoff can seep into the well casing if the well cap seal is worn or if there's settling around the casing. This temporarily increases the water volume the pump has to work against and can cause pressure instability. The fact that your water stays clear is somewhat reassuring here — turbid water after rains would be a stronger sign of surface infiltration — but it's still worth inspecting the well cap and the grout seal around the casing.

What I'd check first:
1. Test the pressure tank as described above
2. Check the air charge in the tank (should be 2 PSI below your cut-in pressure, usually 28 PSI if you're on a 30/50 switch)
3. Look at the well cap and the ground around the casing after the next rain

If the tank checks out fine, the next step is a water test after a rain event to look for coliform or sediment that might indicate infiltration.

What's your cut-in/cut-out pressure setting, and how old is the pressure tank?