i Heat Advisory - Issued within 12 hours of the onset of the following conditions: heat index of at least 105 degrees but less than 115 degrees for less than 3 hours per day. Nighttime lows remain above 80 degrees for 2 consecutive days.
i Ionosphere - Also known as the thermosphere. A layer in the atmosphere above the mesosphere extending from about 80km above the Earth's surface. It can be considered a distinct layer due to a rise in air temperature with increasing height. Atmospheric densities here are very low.