National Weather Service United States Department of Commerce

Strong Winds and Critical Fire Weather Conditions Likely over California

Critical fire weather conditions will continue over portions of California today. Very strong winds with gusts over 60 mph combined with dry humidity values will create an environment conducive to extreme fire danger and explosive fire growth over southern California. Winds are expected to diminish later today and tonight. Read More >

Clouds will be on the increase late tonight, and some patchy fog could develop across parts of the region after midnight. Otherwise, winds will be light and temperatures will generally fall into the 40s tonight.
It'll be a cloudy and wet Monday (for some) across North and Central TX. Afternoon high temperatures will climb into the 50s area-wide with increasing rain chances through the day. The best rain chances will be across Central and East TX. Mostly showers are expected, but a few embedded thunderstorms will also be possible.
A vigorous upper level system will lift across the state late Monday night through Tuesday evening. Plenty of moisture and lift will result in widespread showers and scattered storms, especially across Central Texas. Despite cool surface temperatures in the 60s, the atmosphere will be very dynamic aloft above the cool air. A few stronger storms with frequent lightning, small hail, and localized heavier rainfall & minor flooding are possible along and east of I- 35 and along and south of i-20 from Dallas eastward. At this time, no severe storms are expected.
Forecast models are showing cold air arriving next week around December 22nd and 23rd (on average). What we do not know for sure yet is exactly when the cold air arrives, how cold temperatures will be, and if there will be any precipitation and what kind. We will be providing updates when/as we acquire better confidence in the late week forecast.
Are you shopping or are outdoor activities part of your plans for this upcoming week? Take a look at this week weather outlook. We will have a little bit of everything: rain chances Monday and Tuesday, dry Wednesday and Thursday, and a strong cold front on track for Thursday night and into the holiday weekend. Stay tuned for updates and further details as new data becomes available.

 
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The Heat Index

We, at the National Weather Service, as part of our mission for protecting life and property, have a measure of how the hot weather "feels" to the body. The Heat Index is based on work by R.G. Steadman and published in 1979 under the title "The Assessment of Sultriness, Parts 1 and 2." In this work, Steadman constructed a table which uses relative humidity and dry bulb temperature to produce the "apparent temperature" or the temperature the body "feels".

We use this table to provide you with Heat Index values. These values are for shady locations only. Exposure to full sunshine can increase heat index values by up to 15°F. Also, strong winds, particularly with very hot, dry air, can be extremely hazardous as the wind adds heat to the body. The Heat Index Chart is below.

NWS Heat Index Chart


How to read the chart...Follow the temperature line until it intersects the relative humidity line. Then read the Heat Index on the curved line. For example, an air temperature of 100°F and Relative Humidity of 40%. Follow the 100°F temperature line until it intersects the 40% relative humidity line. Then curved line that also intersects is the Heat Index of 110°F, or Very Hot. That is the temperature the body thinks it is and attempts to compensate for that level of heat. Remember, these values are in the SHADE. You can add up to 15°F to these values if you are in direct sunlight.

The chart below tells you the risk to the body from continued exposure to the excessive heat.

Category Classification Heat Index/Apparent Temperature (°F) General Affect on People in High Risk Groups
I Extremely Hot 130°F or Higher Heat/Sunstroke HIGHLY LIKELY with continued exposure
II Very Hot 105°F - 130°F Sunstroke, heat cramps, or heat exhaustion LIKELY, and heatstroke POSSIBLE with prolonged exposure and/or physical activity
III Hot 90°F - 105°F Sunstroke, heat cramps, or heat exhaustion POSSIBLE with prolonged exposure and/or physical activity
IV Very Warm 80°F - 90°F Fatigue POSSIBLE with prolonged exposure and/or physical activity

 

 

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