I.S. 2 questions

In real world there is no ammeter or voltmeter big enough to measure the size of current & voltage of lightning. However we can measure it indirectly. The following may give you some understanding of the order of current & voltage of lightning.
An average bolt of negative lightning carries a current of 40 kA (kiloamperes), although some bolts can be up to 120 kA, and transfers a charge of 5 coulombs and 500 MJ (megajoules), or enough energy to power a 100 watt lightbulb for just under two months. The voltage depends on the length of the bolt: with the dielectric breakdown of air being 3 million volts per meter, this works out at about one billion volts for a 300m (1,000 feet) lightning bolt.
Different locations have different potentials (voltages) and currents for an average lightning strike. For example, Florida, with the largest number of recorded strikes in a given period, has a very sandy ground saturated with salt water, and is surrounded by water. California, on the other hand, has fewer lightning strikes (being dryer). Arizona, which has very dry, sandy soil and a very dry air, has cloud bases as high as 6,000-7,000 feet above ground level, and gets very long, thin, purplish discharges, which crackle; while Oklahoma, with cloud bases about 1,500-2,000 feet above ground level and fairly soft, clay-rich soil, has big, blue-white explosive lightning strikes, that are very hot (high current) and cause sudden, explosive noise when the discharge comes. The difference in each case may consist of differences in voltage levels between clouds and ground.
The electric currents that flow in return strokes have been measured during direct strikes to instrumented towers. The peak current in a negative first stroke is typically 30 kiloamperes, with a zero-to-peak rise time of just a few microseconds. This current decreases to half-peak value in about 50 microseconds, and then low-level currents of hundreds of amperes may flow for a few to hundreds of milliseconds. The long-continuing currents produce charge transfers on the order of tens of coulombs and are frequently the cause of fires. Subsequent return strokes have peak currents that are typically 10–15 kA, and somewhat faster current rise times. Five percent of the negative discharges to ground generate peak currents that exceed 80 kA, and 5% of the positive discharges exceed 250 kA. Positive flashes frequently produce very large charge transfers, with 50% exceeding 80 coulombs and 5% exceeding 350 coulombs.
I hope this can help with your understanding. =)