Warning Descriptions

 WATCH means that there is a good possibility that the event may happen. When a watch is issued, prepare for the upcoming event. Listen to your local media to know when warnings are issued. Watches are intended to heighten public awareness as to the potential for a particular type of weather.

 WARNING means that conditions for a certain event are imminent. Measures should be taken to safeguard life and property.

Definitions and Criteria

Non-Precipitation Weather
Wind Advisories are issued for sustained winds from 30 to 39 MPH or frequent gusts in the 45 to 57 MPH range for any duration.
High Wind Watches are posted for sustained winds at least 40 mph for at least 1 hour or gusts at least 58 mph for any duration expected beyond 12 hours.
High Wind Warnings are posted for sustained winds at least 40 mph for at least 1 hour or gusts to at least 58 mph for any duration expected within 12 hours.
Dense Fog Advisory may be issued for visibilities 1/4 mile or below. These Advisories are usually posted for widespread fog, not local events such as valley fog.
Excessive Heat Advisories are issued when the Heat Index is expected to reach from 105 to 119 degree Fahrenheit for two consecutive days or longer.
Excessive Heat Warning is issued when the Heat Index is expected to reach 120F or more.
Wind Chill Advisories are posted for wind chills expected from -20F to -34F.
Wind Chill Table
Wind Chill Warnings are posted for wind chills expected from -35F and colder.
Wind Chill Table
Frost and Freeze are most commonly issued during the fall months from late September to early November, except near Lake Erie where these advisories may be needed until late November. During this period, advisories will be issued until the first killing freeze occurs. Warnings will not be needed again until next fall unless during the spring months a late season arctic outbreak threatens vegetation.

Frost Warning describes the formation of thin ice particularly on plants, trees, etc. A Frost Warning will be issued when temperatures are expected to dip between 30 and 35 degrees F.

Freeze and Hard Freeze Warnings describes conditions when the temperature at or near the ground is expected to be a problem to vegetation during the growing season. A Freeze Warning will be posted if temperatures plunge from 25 to around 30 degrees F. A Hard Freeze Warning is issued for temperatures below 25 degrees F.

Air Stagnation Advisories are rare in Ohio. They are usually issued in summer when light winds and dry weather persist. Pollution can reach levels where the public should be notified so they can take precautions.
Winter Weather Safety Tips
Blizzard Warnings are issued if the following conditions are expected to develop. The duration of these conditions must last at least three hours.
  • Sustained winds or frequent gusts of 35 mph or higher.
  • Considerable snowfall or blowing snow (visibilities less than 1/4 mile.)
  • Cold temperatures (usually below 20F, but not always)
Heavy Snow Warning
  • S. OH...at least 4 inches in 12 hours.
  • N. OH and NW PA...at least 6 inches in 12 hours
Ice Storm Warning is issued if freezing rain or drizzle is expected with a significant accumulation of ice (more than 1/4 inch). An ice storm warning indicates that ice will likely accumulate enough to pull down trees and utility lines.
Lake Snow Warning may be issued to cover lake effect snows of 6 or more inches in 12 hours. These events are usually local in nature and confined mainly to the Northern Ohio and Northwest Pennsylvania areas near Lake Erie.
Wind Chill Warning or Advisory is posted specifically for wind chill if no other significant winter weather is expected.

Wind Chill Advisory is issued when wind chill values are expected to be from -20F to -34F.

Wind Chill Warning is issued when wind chill values are expected to be -35 degrees or colder.

Wind Chill Chart

A Winter Storm Watch may be issued for an event expected to have one or more frozen or freezing precipitation hazards. A watch is usually issued to give 12 to 48 hour notice.

A Winter Storm Warning , is issued when two or more frozen or freezing precipitation hazards are anticipated within the next 12 hours. Example: If you have Lake Snow Warning conditions along with Wind Chill Warning conditions, a Winter Storm Warning will be issued.

Advisories are issued when events are expected to remain below the warning criteria, but still cause significant inconvenience.

Snow Advisory is issued for:
  • 3 to 5 inches in Northern Ohio and Northwest PA
  • 2 to 4 inches in Central and Southern Ohio

A forecaster may issue a snow advisory for the first snow of the season or first snow in several days for a lighter snowfall.

Blowing Snow Advisory is posted when surface visibility is intermittently reduced to 1/4 mile or less because of blowing snow.
Lake Snow Advisory has the same criteria as a Snow Advisory, except that it is issued for Lake Effect Snow situations only.
Wind Chill Advisory

Wind Chill Warning
Freezing Rain or Freezing Drizzle Advisory is issued when hazardous driving conditions are expected.
Winter Weather Advisory is issued when two or more winter weather hazards are expected together.
Severe Weather Safety Tips
A Severe Thunderstorm or Tornado Watch means that conditions favor severe weather in and near the watch area. These watches are issued by the Storm Prediction Center in Kansas City, MO. Watches are intended to heighten public awareness and should not be confused with warnings.
Tornado Warning is issued if
  • a tornado is spotted on the ground
  • a funnel cloud is spotted
  • a rotating wall cloud is observed
  • radar shows a rotating thunderstorm or hook echo
Severe Thunderstorm Warning is issued if a particular thunderstorm is thought to contain
  • Damaging straight-line winds of 58 mph or greater
  • Hail 3/4 inch diameter or larger -- Golf ball sized
Severe thunderstorms sometimes produce tornadoes without warning.
Flooding Safety Tips
Flood Watch is issued when rainfall is expected to exceed flood guidance. A flood watch means that widespread general flooding is possible.
Flash Flood Watch is issued when rainfall is expected to exceed flash flood guidance. A flash flood watch means that rapid rises in streams and rivers are possible, which may pose a serious threat to life and property.
Flash Flood Warning means that a rapid rise in streams and rivers is imminent or already in progress. Rivers will likely overflow their banks within 6 hours of the heavy rains. A dam failure would also warrant a flash flood warning.
Flood Warning means that a rise in streams and rivers is imminent or already underway. Rivers will likely go out of their banks.
Urban and Small Stream Flood Warning means that the rainfall is so heavy that drainage systems and small creeks cannot carry the run-off fast enough. Water may backup into yards and streets. The high water may damage property, but is usually not life-threatening. The flooding is usually short-lived and not widespread, and usually does not result in the flooding of rivers.
River Flood Warning is issued when a particular river at a particular point is expected to overflow its banks.
Special Marine Warning is a short term warning typically used during the spring and summer. These are issued for thunderstorms or winds exceeding 34 knots expected to last less than two hours. Boaters should move to safe harbor if threatening weather approaches.
Small Craft Advisory is issued exclusively for the nearshore waters when waves are expected to average four feet or greater.
Gale Warning is issued for the entire lake when winds are forecast between 35 and 49 knots for more than two hours.
Storm Warning is posted whenever winds on the lake exceed 50 knots.

Wind Chill

Temperature (F)
Wind (knots) 40 35 30 25 20 15 10 5 0 -5 -10 -15 -20 -25 -30
5 36 30 25 19 14 8 3 -2 -8 -13 -19 -24 -30 -35 -40
10 26 20 13 7 1 -6 -12 -18 -25 -31 -37 -44 -50 -56 -63
15 20 13 6 -1 -7 -14 -21 -28 -35 -42 -49 -56 -63 -70 -77
20 16 9 2 -6 -13 -20 -28 -35 -42 -50 -57 -64 -72 -79 -86
25 13 6 -2 -9 -17 -25 -32 -40 -47 -55 -63 -70 -78 -85 -93
30 11 4 -4 -12 -20 -28 -35 -43 -51 -59 -66 -74 -82 -90 -98
35 10 2 -6 -14 -22 -30 -37 -45 -53 -61 -69 -77 -85 -93 -101
40 9 1 -7 -15 -23 -31 -39 -47 -55 -63 -71 -79 -87 -95 -103

Wind Chill is the cooling effect of temperature and wind. The index is based on the cooling rate of a nude body in the shade. The index is only an approximation because individual bodies vary in shape, size, and metabolic rate.

Interpretation: At a given temperature and wind speed, the wind chill index estimates at what temperature a body would lose heat at the same rate without any wind.

For example, if the temperature is 25 degrees and the wind blows at 20 knots, your body would lose heat at the same rate as if the temperature were -6 with no wind.

Remember, mph = knots / 1.15.