Extreme Weather
Extreme weather includes extreme heat or cold events, wind events, and atmospheric river events, characterized by intense periods of heavy rain. The National Weather Service (NWS) identifies threats based on severity of likely impacts, and the anticipated risk.
Extreme Heat is one of the leading weather-related killers in the United States, resulting in hundreds of fatalities each year. Heat is associated with lower air quality and may combine with an increased likelihood for planned or unplanned power outages.
Extreme Cold affects millions of people across the United States. Individuals and families who are unsheltered or who lack access to heating may be disproportionately impacted.
Atmospheric rivers may cause flooding, damage infrastructure and make transportation more dangerous. Floods are the most common and widespread of all weather-related natural disasters. Flash floods are the most dangerous kind of floods, because they combine the destructive power of a flood with incredible speed. Flash floods occur when heavy rainfall exceeds the ability of the ground to absorb it. They also occur when water fills normally dry creeks or streams or enough water accumulates for streams to overtop their banks, causing rapid rises of water in a short amount of time. They can happen within minutes of the causative rainfall, limiting the time available to warn and protect the public.
High winds can occur during a severe thunderstorm, with a strong weather system, or can flow down a mountain. When winds are sustained at 40-50 mph, isolated wind damage is possible. Widespread significant wind damage can occur with higher wind speeds.
The city may take action when extreme weather is anticipated. City actions take into account NWS products and risks, and align with the City Emergency Operations Plan(PDF, 1MB). Read more in the drop-down menu below about keeping yourself and your family safe during extreme weather events.
What Can You do? Prepare for Extreme Heat
Heat is one of the leading weather-related killers in the United States, resulting in hundreds of fatalities each year. Heat can be very taxing on the body; check out the heat related illnesses that can occur with even a short period of exposure. Everyone can be vulnerable to heat, but some more so than others. According to The Impacts Of Climate Change On Human Health In The United States: A Scientific Assessment some groups are particularly vulnerable to heat; check in with friends and relatives who fall in one of these populations, especially if they don’t have air conditioning.
People and pets may be more susceptible to heat effects. Stay hydrated, take cooling breaks, and never leave people or pets unattended in hot vehicles! County libraries, including the Cupertino Library, are available during regular business hours as places where people can go to get cool.
Follow Tips to stay safe:
Outdoor Activities
- Slow down. Reduce, eliminate or reschedule strenuous activities until the coolest time of the day. Those particularly vulnerable to heat such as children, infants, older adults (especially those who have preexisting diseases, take certain medications, living alone or with limited mobility), those with chronic medical conditions, and pregnant women should stay in the coolest available place, not necessarily indoors.
- Dress for summer. Wear lightweight, loose fitting, light-colored clothing to reflect heat and sunlight.
- Minimize direct exposure to the sun. Sunburn reduces your body's ability to dissipate heat.
Eating and Drinking
- Eat light, cool, easy-to-digest foods such as fruit or salads. If you pack food, put it in a cooler or carry an ice pack. Don't leave it sitting in the sun. Meats and dairy products can spoil quickly in hot weather.
- Drink plenty of water (not very cold), non-alcoholic and decaffeinated fluids, even if you don't feel thirsty. If you are on a fluid-restrictive diet or have a problem with fluid retention, consult a physician before increasing consumption of fluids.
- Do not take salt tablets unless specified by a physician.
Cooling Down
- Use air conditioners or spend time in air-conditioned locations such as malls and libraries.
- Use portable electric fans to exhaust hot air from rooms or draw in cooler air.
- Do not direct the flow of portable electric fans toward yourself when room temperature is hotter than 90°F. The dry blowing air will dehydrate you faster, endangering your health.
- Take a cool bath or shower.
Check on Others
- Check on older, sick, or frail people who may need help responding to the heat. Each year, dozens of children and untold numbers of pets left in parked vehicles die from hyperthermia. Keep your children, disabled adults, and pets safe during tumultuous heat waves.
- Don't leave valuable electronic equipment, such as cell phones and gps units, sitting in hot cars.
- Make sure rooms are well vented if you are using volatile chemicals.
- For more heat health tips, go to the Centers for Disease Control and Prevention
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What Can You do? Prepare for Extreme Cold
Extreme Cold Safety
Extremely cold air comes every winter in at least part of the country and affects millions of people across the United States. The arctic air, together with brisk winds, can lead to dangerously cold wind chill values. People exposed to extreme cold are susceptible to frostbite in a matter of minutes. Areas most prone to frostbite are uncovered skin and the extremities, such as hands and feet. Hypothermia is another threat during extreme cold. Hypothermia occurs when the body loses heat faster than it can produce.
General Information
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Keep a winter survival kit in your vehicle if you must travel.
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Check tire pressure, antifreeze levels, heater/defroster, etc.
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Learn how to shut off water valves for potential pipe bursts.
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Check on the elderly.
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Bring pets inside.
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Stay indoors during the coldest times (late evening and early mornings)
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Minimize travel.
How Should I Dress?
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Wear layers of loose-fitting, lightweight, warm clothing, and a hat.
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Mittens, snug at the wrist, are better than gloves.
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Cover your mouth to protect your lungs from extreme cold.
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Try to stay dry and out of the wind.
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What can you do? Prepare for Wind and Rain Events
National Weather Service Messaging Terminology
- FLASH FLOOD WATCH or FLOOD WATCH
Flash flooding or flooding is possible within the designated watch area — be alert.
- FLASH FLOOD WARNING or FLOOD WARNING
Flash flooding or flooding has been reported or is imminent — take necessary precautions at once! Get to higher ground!
- Turn around, don’t drown! Most fatalities in the US from flash flooding are from vehicles driving into flooded roadways.
- URBAN and SMALL STREAM ADVISORY
Flooding of small streams, streets and low-lying areas, such as railroad underpasses and urban storm drains is occurring.
- FLASH FLOOD STATEMENT or FLOOD STATEMENT
Follow-up information regarding a flash flood/flood event
What can you do? Prepare for Thunderstorms
Lightning: What You Need to Know
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NO PLACE outside is safe when thunderstorms are in the area!!
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If you hear thunder, lightning is close enough to strike you.
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When you hear thunder, immediately move to safe shelter: a substantial building with electricity or plumbing or an enclosed, metal-topped vehicle with windows up.
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Stay in safe shelter at least 30 minutes after you hear the last sound of thunder.
Indoor Lightning Safety
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Stay off corded phones, computers and other electrical equipment that put you in direct contact with electricity.
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Avoid plumbing, including sinks, baths and faucets.
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Stay away from windows and doors, and stay off porches.
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Do not lie on concrete floors, and do not lean against concrete walls.
Last Resort Outdoor Risk Reduction Tips
If you are caught outside with no safe shelter anywhere nearby the following actions may reduce your risk:
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Immediately get off elevated areas such as hills, mountain ridges or peaks
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Never lie flat on the ground
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Never shelter under an isolated tree
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Never use a cliff or rocky overhang for shelter
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Immediately get out and away from ponds, lakes and other bodies of water
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Stay away from objects that conduct electricity (barbed wire fences, power lines, windmills, etc.)
What is the City doing? City Actions
The City prepares for the potential of extreme weather throughout the year. The Office of Emergency Management (OEM) works with other City departments to build and maintain emergency plans to support a more efficient response to an extreme weather event. The City provides emergency preparedness training to the community and City staff. The City shares information about hazard mitigation and engages with resident volunteers to be ready for an extreme weather event. These things help to mitigate the potential impacts of an extreme weather event.
Proactive extreme weather actions
The City Public Works Department works throughout the year to maintain streets and sidewalks, keep gutters and storm drains clear, and to maintain the City infrastructure we rely on. Public Works maintains trees and street medians, reducing the potential for impacts from falling tree limbs during a wind event. Public Works responds every day to requests for service through the 311 application.
When extreme weather is forecast
When extreme weather is forecast, the City responds based on the type and severity of weather forecast by the National Weather Service, and taking into account other factors which may contribute to more serious weather impacts.
If rain may cause localized flooding, Public Works will fill and distribute sandbags for residents. During an extreme weather event, Public Works continues to monitor and respond to service requests through 311 including requests related to impacts of extreme weather.