Weather Guide

Severe thunderstorms are defined by the National Weather Service as storms producing winds of 58 mph or greater, hail one inch in diameter or larger, or tornadoes. In the United States, roughly 100,000 thunderstorms occur each year, and about 10% are classified as severe. They're most common in spring and summer, particularly in the central and southeastern states, but can occur anywhere.

The first step in preparation is awareness. Check the hourly forecast before any outdoor activity that will last more than an hour. If you see a thunderstorm code (WMO codes 95–99) in the next few hours, plan accordingly. The 30-30 rule is a useful field guide: if the time between a lightning flash and the thunder that follows is 30 seconds or less, the storm is within 6 miles — seek shelter immediately. Stay sheltered for 30 minutes after the last thunder.

At home, prepare a basic storm kit: a battery-powered or hand-crank weather radio, flashlights, extra batteries, a first aid kit, and at least three days of water and non-perishable food. Surge protectors guard electronics against power spikes. Unplug sensitive equipment if a severe storm is imminent — a surge protector helps with minor fluctuations but won't stop a direct lightning strike on your power line.

If you're caught outdoors, avoid tall isolated trees, open fields, hilltops, and bodies of water. Move to a substantial building or a hard-topped vehicle. Convertibles, open-sided shelters, and small sheds offer no meaningful protection. If no shelter is available and lightning is imminent, crouch low on the balls of your feet, minimize your contact with the ground, and stay away from other people — a group increases the risk of ground current injuries.

Air temperature is a single number that describes the energy content of the air around you — but your body's experience of that temperature depends on several other factors working simultaneously. Understanding them helps you interpret forecasts more accurately and dress more appropriately.

Humidity is the biggest modifier. Your body cools itself primarily through sweat evaporation. When the air is already saturated with moisture — high relative humidity — sweat evaporates slowly, and your body retains heat. At 75°F and 90% humidity (common in coastal cities and the Gulf South), the heat index pushes the apparent temperature above 80°F. At 75°F and 20% humidity (common in the desert Southwest), evaporative cooling works efficiently and the air feels comfortable or even slightly cool in the shade.

Wind speed is the second major factor. Moving air accelerates evaporation from your skin and carries heat away from your body faster than still air. This is why a breezy 65°F day can feel colder than a calm 55°F day in a sheltered spot. Wind chill calculations formalize this effect — the NWS wind chill formula accounts for both temperature and wind speed to estimate the rate of heat loss from exposed skin.

Elevation affects temperature through the adiabatic lapse rate — air cools roughly 3.5°F for every 1,000 feet of altitude gain. Denver at 5,280 feet is typically 18°F cooler than a sea-level city at the same latitude. Solar radiation is also more intense at altitude because there's less atmosphere to filter it, so a sunny 60°F day in the mountains can feel warm in direct sun and cold in the shade simultaneously.

Urban density creates the heat island effect. Asphalt, concrete, and rooftops absorb solar radiation during the day and release it slowly at night, keeping cities 2–7°F warmer than surrounding rural areas. This is why city residents often experience warmer overnight lows than suburban or rural neighbors even when daytime highs are similar.

The most common travel weather mistake is checking a 7-day forecast too early. Beyond 4–5 days, daily temperature forecasts carry significant uncertainty — a predicted rainy Thursday might shift to Friday, or clear up entirely. For trips more than a week out, focus on the seasonal climate of your destination rather than specific daily forecasts. Look up average highs, lows, and precipitation for that month to set realistic expectations.

Within 48–72 hours of travel, hourly forecasts become genuinely reliable. This is the window to check conditions for your arrival day, any outdoor activities you've planned, and your departure. Pay attention to the feels-like temperature, not just the air temperature — a 50°F day with 30 mph winds and rain is a very different experience from a calm, sunny 50°F afternoon.

For road trips, check weather along your entire route, not just at your destination. Mountain passes, coastal highways, and plains corridors can have dramatically different conditions than either end of your journey. A clear day at your origin and destination can still mean navigating fog, ice, or severe storms somewhere in between.

Time & Temp's city search makes it easy to check any destination worldwide. Type the city name into the search box on the home page to get current conditions and a 7-day forecast for anywhere on the planet. Use it to check your hotel's city, any day-trip destinations, and your home city for the return trip.