Individual solar cells are somewhat difficult to solder to. Self-adhesive metal stained-glass tape makes for the easiest soldering job--the tape holds itself in place while you solder. Use electronics solder that contains 2% silver. One side of the cell is (+), the other (-).
rain check (plural rain checks) (idiomatic) Any voucher or note from a merchant to a customer to provide an item the merchant has run out of at a later date for the item's current price, or (in a more literal sense) to provide a service at a later date.
A rain gauge is an instrument for measuring the precipitation that has fallen in a given time interval. The rain gauge is part of every weather station. It is used in meteorology as an additional tool of the weather forecast and the climatology for the purpose of long-term statistics of precipitation.