The co-author of a 2005 study on the relationship between weather and presidential elections says the growing trend to early voting will lessen the impact of weather on voter turnout.

The weather has become more of a factor since lawmakers originally selected the first Tuesday in November to hold the presidential election. The fledgling nation was mainly an agrarian society, and November was likely the most suitable month for farmers and residents of the mostly rural original 13 states.

The fall harvest was complete, and the weather along the Eastern Seaboard was usually mild enough for voters to endure sometimes difficult travel over unimproved roads, where there were roads at all.

As the nation grew, the weather on Election Day began to exert its influence. As Expert Senior Meteorologist John Kocet says, "In early November, there can be huge blizzards across the Great Plains, subzero temperatures in the northern Plains and powerful storms in the Pacific Northwest."

Nothing out of the ordinary is expected as far as weather is concerned on Tuesday. The Southwest, the balance of the Plains, and Northeast will stay dry and mild to warmer than normal.

Some rain and mountain snow showers are in the forecast in the Pacific Northwest and the northern Rockies. The northern Plains and Southeast coast will also have a chance for some rain.

History says that Tuesday's forecast should favor Democratic candidate Barack Obama. A 2005 study published in the June 2007 edition of the Journal of Politics concluded that poor weather on Election Day favors the Republican party.

One of the co-authors of the study, University of Pittsburgh political science professor George Krause,

Early voters brave chilly weather in anticipation of a long wait outside the polling place at Spruill Oaks library Tuesday, Oct. 28, 2008, in Johns Creek, Ga. (AP Photo/John Amis)

tells AccuWeather.com that the growing trend of early voting could lessen the impact of weather on the first Tuesday of November.

The study examined the effect of weather on voter turnout in 14 U.S. presidential elections and determined that Democrats are less likely to vote in inclement weather. Professor Krause says rain is a bigger deterrent for many voters than cold temperatures.

"Many voters are more willing to stand in line on a cold, clear day. That is not the case if it is raining." He adds that many peripheral voters tend to vote Democrat, are "less dependable" and less likely to turn out on Election Day if the weather is less-than-ideal.

More Democrats either walk or take public transit to polling stations in large cities and urban areas where a rainy or snowy day could discourage them from standing in long lines at busy polling places.

The study concluded that rain reduced voter turnout by a rate of just under 1 percent per inch, while voter turnout dropped by almost one-half of one percent for each inch of snow.

Dr. Krause feels that the increased use of early voting across the country is becoming a mitigating factor on the impact of weather on the election. While the first Tuesday in November could produce extreme weather in many parts of the country, he says voters can use unrestricted early voting to avoid having to stand in line in the rain, snow or cold.

At least 32 states this year allow some form of no-excuse early voting, according to electionline.org. Reports from across the country say that there have been huge lines at early polling stations. In Florida, Gov. Charlie Crist had to issue an executive order extending early voting hours statewide from eight hours a day to twelve.

The Obama campaign said Friday that early voting totals in battleground states are heavily Democratic, adding that John McCain must win big on Tuesday to become President.

Campaign manager David Plouffe said in a conference call with reporters, Sen. Obama is running strong in the swing states of Florida, Colorado, New Mexico and others.

Republican candidate Sen. John McCain told supporters at a rally in Ohio on Friday, "The pundits have written us off much as they have done before, but we are closing my friends, and we are going to win Ohio."