We are used to Lou Cannon's venting his spleen against President Reagan. But need he go so far as to seem to question the president's "present state of mind"?

What occasions this vituperation in Cannon's column of Aug. 17 is the president's alleged inability to deviate from the TelePrompter. Claims Cannon: "Left to his own devices, the Great Communicator no longer exists."

Proof? Cannon quotes the president as having "wandered away" from his script in Wisconsin on July 27, as follows:

"You know, a president some years ago was talking about government and its power, and he said, 'If the people don't know enough to run their own lives, where do we find a little select elite that cannot only run their lives themselves but the people's lives for them. And that is government?' Well, you can't find them."

The president was apparently paraphrasing Thomas Jefferson's First Inaugural statement:

"Sometimes it is said that man cannot be trusted with the government of himself. Can he, then, be trusted with the government of others? Or, have we found angels in the form of kings to govern him?"

It seems to me that President Reagan's paraphrase is reasonably accurate for an off-the-script remark, and that Cannon owes the president an apology. -- William H. Peterson Weather Report I am very upset and disappointed with your new weather forecast. For years I have checked in your daily report the weather from Fairbanks, Alaska, where I have children and grandchildren. I would prefer seeing you print temperatures of the good ol' U.S.A. rather than such places as Reykjavik, Riyadh, La Paz, etc.

Incidentally, your national forecast map does not include our 49th and 50th states: Hawaii and Alaska. -- Ruth Sikorski

I love your new weather section. You have made a supreme effort to cover the nation's weather in detail. But for a newspaper that is usually so careful about presenting misleading picture angles, you have come up with the strangest map projection I have ever seen. Somewhere around Nebraska the earth's curve suddenly changes, causing Oregon and West Virginia to appear to be about the same size.

Your national weather map reminds me of the famous New Yorker cover showing a New York City resident's perception of the lack of importance of the rest of the country relative to his home.

-- Denny Miles

While your new weather page does have some interesting new features, would you please resume printing of the Potomac River stage at Little Falls? On any day, there are probably more local canoeists, kayakers, fishermen, etc. whose plans are directly affected by the river water level than there are local persons interested in today's weather forecast for Boise and Auckland. -- Andrew L. Dannenberg

I welcome the expanded weather roundup -- with one glaring exception. The new format omits an essential set of data by not including the previous day's temperatures for selected cities.

The explanation is that the new format "should be of greater use for travelers." But not all of us use the weather page for travel purposes. Some of us are mere weather enthusiasts who use the page to follow the latest Midwest heat wave or Great Plains cold snap. What better way is there to do this than by looking first at yesterday's temperatures and then looking to forecasted highs and lows?

Wouldn't it be odd if the rest of The Post also stopped reporting yesterday's news? -- Bradley R. Rippey Who 'Holed' That Tanker? Your editors' heads must have been "holed" when they allowed Loren Jenkins {"Tanker Convoy Reachers Kuwait . . .," Aug. 12} to write "that the mine that holed the 117,200-ton Texaco Caribbean. . . ."

"Verbing" is becoming so popular that the one "incidented" aberration might have been overlooked, but consider: "Administration sources in Washington said Tuesday that Kuwait and Saudi Arabia in recent days have been quietly assisting in minesweeping operations. . . ." Yes, and later, administration sources said "Wednesday"! Why not, "On Tuesday administration sources in Washington said . . ."? "In recent days" means "recently," and "minesweeping" unadorned is an "operation."

Jenkins says "mines were laid by Iran to try to hamper the U.S. convoys." They were "laid to hamper," and they did. Just before that bit of sentence stuffing, we read: "The Omani mine hunters . . . established the mines were the same type . . ." The mine hunters established that the mines were of the same type. And still later we read that "authorities here are dismissive of the mine threat." Why not, "authorities here dismiss the mine threat"? Again, we read "that on any given day. . . ." Any day is a given!

Finally, a parenthetical paragraph tells us that "NBC News reported that the helicopter carrier . . . has broken down" when it really "had broken down" in concordance with tense.

-- Ron Bourgea

Not Burgundy (Cont'd.) Jim Steele {Free for All, Aug. 15} says the Redskins' colors are burgundy and gold. Actually, before they were the Boston Redskins they were called the Marooners. I can't recall who they played for then. It was, I think, a nonprofessional team. But it seems that their correct colors really are maroon and gold. -- Mary Marsico