* Injection estimates range from 67 to 103 bcf
* Median build in the Reuters poll is 79 bcf (Adds weather data, background, table)
NEW YORK, Sept 22 (Reuters) - U.S. natural gas storage levels on average are expected to rise by 80 billion cubic feet when weekly data from the U.S. Energy Information Administration are released early Thursday.
In the weekly Reuters survey of 27 industry traders and analysts, injection estimates for the week ended Sept. 17 ranged from 67 to 103 bcf.
Stocks rose an adjusted 66 bcf for the same week last year, while the five-year average gain for that week is 70 bcf.
The median build in the survey was 79 bcf.
The EIA storage report will be issued Thursday at 10:30 a.m. EDT (1430 GMT).
The U.S. National Oceanic and Atmospheric Administration said there were 41 cooling degree days last week, unchanged from the previous week but four warmer than normal and three warmer than the same week last year.
Degree days, a measure of departure in the mean daily temperature from 65 degrees Fahrenheit (18 Celsius), are used to reflect demand for energy to heat or cool homes and businesses.
Record heat and power demand this summer slowed storage builds by about 16 percent from June through August, with a total of about 740 bcf injected versus a five-year average of about 880 bcf for the same three months.
But milder September weather has opened the door to bigger inventory builds. Last week's injection was the first in 13 weeks to exceed the five-year average, and most players expect to see more above-average gains in coming weeks.
In the last report for the week ended Sept. 10, overall storage rose 103 bcf, well above the Reuters survey estimate of 90 bcf, the year-ago gain of 67 bcf and the five-year average increase for that week of 77 bcf.
The report showed total domestic gas inventories climbed to 3.267 trillion cubic feet, 182 bcf, or 5 percent, below last year's record high but a level not normally reached until late September.
The weekly build widened the inventory surplus to the five-year average by 26 bcf to 192 bcf, a comfortable 6 percent cushion for rebuilding stocks for next winter.
Eastern storage climbed 54 bcf in the last report but held at about 6 percent below last year's levels.
Consuming Region West storage, which rose 13 bcf for the week, edged up to 4 percent above the same year-ago week.
Inventories in the Producing Region gained 36 bcf and climbed to about 9 percent below the same week in 2009.
A total build Thursday at the Reuters survey estimate would narrow the deficit to last year to 168 bcf and widen the surplus to the five-year average to about 202 bcf.
In the last four reports, total stocks rose 255 bcf, or about 64 bcf per week, versus a 252-bcf adjusted increase for the same one-month period last year and a 259-bcf five-year average gain for that period.
NOAA said it expected 47 cooling degree days this week, 18 warmer than normal and six warmer than the same year-ago week.
Early injection estimates for next week's EIA report range from 82 bcf to 88 bcf, versus a 65 bcf build for the same week last year and a five-year average gain of 67 bcf.
If weekly builds through October match the five-year average pace, inventories will begin next heating season with 3.675 tcf in the ground, 4 percent below last November's record high but still nearly 6 percent above average.
To get inventories above last year's high of 3.837 tcf by Nov. 1, weekly injections must average 81 bcf for the remaining 7 weeks of the stock building season, well above the five-year average of 58 bcf for that period.
The following is a partial list of forecasters who participated in this week's survey. If forecasters provided a range, the midpoint was used. Numbers in billion cubic feet (bcf).
Advantage IQ + 79
Caprock + 77
Credit Suisse + 69
CH Guernsey + 103
Citi Futures + 88
Energy Mgmt Inst + 84
enerjay + 86
FirstEnergy + 83
First Enercast + 71
Hencorp + 68
Gelber & Assoc + 90
IAF Advisors + 71
JPMorgan + 73
Lind-Waldock + 85
MF Global + 88
PFGBest + 67
Prestige Economics + 85
Raymond James + 83
Ritterbusch & Assoc + 68
SMC Forecasting + 90
Stephen Smith Energy + 75
Strategic Energy + 72
Summit Energy + 89
Tradition Energy + 78