Warman Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Warman Observatory clear sky chart from 2005-11-06 to 2024-01-13.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	13% 9% 4 7% 6% 3 5% 5% 5% 7% 36%	75255
	Night	12% 9% 4 7% 6% 3 5% 4 5% 7% 38%	74505
Transparency	Day	46% 7% 13% 23% 10% 1	74949
	Night	45% 6% 13% 23% 11% 1	74332
Seeing	Day	16% 9% 30% 28% 14% 4	14886
	Night	16% 8% 31% 32% 11% 1	24923

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	7% 11% 5% 10% 10% 5% 6% 4 5% 7% 29%	1517
	11th to 20th	Day	9% 13% 7% 12% 9% 4 5% 6% 7% 7% 22%	1461
	21st to end	Day	9% 12% 7% 12% 8% 5% 6% 6% 6% 9% 21%	1756
February	1st to 10th	Day	9% 11% 5% 9% 7% 4 5% 4 4 7% 35%	1620
	11th to 20th	Day	7% 10% 5% 8% 8% 4 5% 4 5% 7% 36%	1574
	21st to end	Day	9% 13% 4 8% 7% 3 6% 5% 5% 7% 33%	1368
March	1st to 10th	Day	12% 11% 5% 7% 7% 3 5% 5% 5% 7% 34%	1926
	11th to 20th	Day	14% 9% 4 6% 5% 4 4 5% 6% 8% 36%	1980
	21st to end	Day	18% 10% 4 8% 7% 3 4 5% 4 7% 30%	2200
April	1st to 10th	Day	17% 9% 3 7% 6% 4 5% 5% 4 6% 34%	2160
	11th to 20th	Day	19% 11% 4 8% 5% 3 3 4 5% 6% 31%	2172
	21st to end	Day	22% 9% 4 7% 5% 3 5% 4 4 6% 32%	2340
May	1st to 10th	Day	17% 8% 3 7% 7% 4 5% 4 4 6% 35%	2466
	11th to 20th	Day	17% 6% 3 5% 6% 3 6% 5% 5% 7% 37%	2479
	21st to end	Day	15% 6% 3 7% 6% 3 4 5% 5% 8% 38%	2725
June	1st to 10th	Day	11% 5% 2 5% 5% 3 5% 5% 6% 8% 45%	2520
	11th to 20th	Day	13% 5% 3 6% 6% 3 6% 5% 5% 9% 40%	2676
	21st to end	Day	9% 5% 2 5% 6% 4 6% 7% 7% 11% 38%	2700
July	1st to 10th	Day	6% 3 2 4 5% 2 4 5% 6% 10% 52%	2700
	11th to 20th	Day	8% 5% 2 5% 4 3 5% 5% 7% 9% 47%	2538
	21st to end	Day	7% 4 2 4 5% 3 5% 6% 6% 9% 51%	2743
August	1st to 10th	Day	9% 4 2 5% 6% 4 6% 5% 7% 9% 44%	2342
	11th to 20th	Day	13% 5% 3 5% 5% 3 4 5% 5% 8% 45%	2301
	21st to end	Day	11% 5% 2 4 4 3 4 4 5% 9% 49%	2484
September	1st to 10th	Day	9% 5% 3 5% 5% 3 4 5% 6% 9% 44%	2160
	11th to 20th	Day	11% 6% 3 5% 5% 3 5% 5% 5% 7% 45%	2132
	21st to end	Day	14% 8% 2 5% 6% 3 4 4 6% 7% 41%	1895
October	1st to 10th	Day	18% 8% 2 6% 5% 3 4 5% 5% 7% 37%	1800
	11th to 20th	Day	16% 11% 3 8% 5% 3 5% 5% 4 6% 34%	1800
	21st to end	Day	19% 10% 4 7% 5% 3 4 4 4 6% 33%	1936
November	1st to 10th	Day	14% 11% 5% 10% 7% 3 4 4 5% 5% 33%	1523
	11th to 20th	Day	12% 14% 8% 11% 8% 4 4 5% 4 5% 25%	1520
	21st to end	Day	13% 12% 5% 7% 7% 3 5% 5% 6% 7% 30%	1520
December	1st to 10th	Day	11% 14% 5% 10% 10% 5% 7% 4 5% 6% 23%	1520
	11th to 20th	Day	11% 14% 5% 11% 9% 4 5% 5% 6% 5% 26%	1918
	21st to end	Day	22% 18% 5% 8% 8% 3 4 4 4 4 18%	2783
January	1st to 10th	Night	9% 8% 4 10% 9% 5% 4 4 6% 7% 32%	2648
	11th to 20th	Night	10% 13% 6% 10% 7% 3 5% 5% 6% 8% 28%	2561
	21st to end	Night	11% 12% 6% 11% 8% 4 5% 6% 6% 6% 25%	2596
February	1st to 10th	Night	6% 9% 5% 9% 7% 4 5% 5% 5% 7% 37%	2340
	11th to 20th	Night	7% 9% 4 8% 6% 4 5% 5% 6% 6% 39%	2273
	21st to end	Night	12% 9% 4 7% 6% 4 5% 5% 6% 7% 34%	1888
March	1st to 10th	Night	11% 11% 4 7% 6% 4 5% 5% 4 5% 37%	2048
	11th to 20th	Night	13% 9% 3 6% 6% 3 3 4 5% 6% 41%	1980
	21st to end	Night	17% 9% 3 6% 6% 3 5% 3 5% 7% 35%	2155
April	1st to 10th	Night	17% 11% 4 5% 5% 3 4 5% 4 5% 37%	1800
	11th to 20th	Night	20% 10% 4 6% 4 3 4 3 5% 5% 35%	1733
	21st to end	Night	19% 9% 4 6% 5% 3 5% 5% 4 6% 34%	1620
May	1st to 10th	Night	15% 9% 4 6% 5% 2 4 4 5% 6% 40%	1494
	11th to 20th	Night	15% 6% 3 5% 4 3 5% 5% 5% 8% 42%	1416
	21st to end	Night	13% 5% 3 5% 5% 2 4 5% 8% 9% 41%	1551
June	1st to 10th	Night	11% 4 2 5% 4 4 5% 4 7% 9% 44%	1440
	11th to 20th	Night	10% 5% 2 5% 5% 4 5% 5% 6% 8% 45%	1278
	21st to end	Night	9% 3 3 5% 5% 4 4 4 6% 8% 49%	1260
July	1st to 10th	Night	2 4 2 3 4 2 5% 5% 6% 10% 57%	1260
	11th to 20th	Night	7% 4 2 4 4 3 4 4 6% 6% 56%	1417
	21st to end	Night	4 2 2 4 3 3 3 4 5% 9% 60%	1575
August	1st to 10th	Night	6% 4 2 4 4 3 4 5% 6% 9% 53%	1593
	11th to 20th	Night	12% 5% 2 4 3 2 3 4 6% 7% 52%	1600
	21st to end	Night	10% 6% 2 4 4 3 3 3 5% 8% 51%	1870
September	1st to 10th	Night	9% 4 2 4 4 3 3 5% 5% 8% 54%	1800
	11th to 20th	Night	9% 5% 1 4 5% 3 4 5% 5% 8% 52%	1826
	21st to end	Night	15% 4 2 4 4 3 4 3 5% 7% 47%	2047
October	1st to 10th	Night	15% 7% 2 5% 4 3 4 4 4 6% 45%	2160
	11th to 20th	Night	15% 10% 4 6% 5% 3 5% 4 5% 6% 38%	2160
	21st to end	Night	17% 11% 4 8% 5% 3 3 4 4 6% 34%	2419
November	1st to 10th	Night	14% 8% 4 8% 6% 4 5% 5% 5% 7% 36%	2554
	11th to 20th	Night	14% 10% 5% 9% 7% 4 6% 5% 5% 6% 29%	2660
	21st to end	Night	12% 8% 5% 7% 6% 4 6% 6% 5% 7% 34%	2660
December	1st to 10th	Night	10% 12% 5% 12% 7% 4 7% 5% 6% 7% 26%	2660
	11th to 20th	Night	11% 13% 6% 10% 8% 4 6% 5% 6% 6% 25%	3279
	21st to end	Night	23% 17% 5% 8% 5% 3 4 3 4 5% 22%	4884

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	55% 6% 10% 21% 8% 1	1518
	11th to 20th	Day	58% 8% 10% 15% 8%	1461
	21st to end	Day	59% 5% 12% 15% 8% 1	1756
February	1st to 10th	Day	50% 5% 11% 23% 10% 2	1620
	11th to 20th	Day	48% 6% 14% 23% 8% 1	1583
	21st to end	Day	51% 6% 11% 20% 12% 1	1368
March	1st to 10th	Day	50% 7% 15% 20% 8% 1	1926
	11th to 20th	Day	45% 7% 16% 23% 9% 1	1980
	21st to end	Day	53% 6% 10% 21% 8% 1	2200
April	1st to 10th	Day	50% 5% 11% 19% 12% 1	2160
	11th to 20th	Day	55% 5% 9% 18% 12% 1	2172
	21st to end	Day	54% 6% 11% 19% 10%	2340
May	1st to 10th	Day	49% 6% 12% 22% 9% 2	2466
	11th to 20th	Day	45% 8% 14% 22% 10% 1	2483
	21st to end	Day	44% 7% 12% 24% 11% 1	2725
June	1st to 10th	Day	35% 7% 17% 30% 10% 1	2520
	11th to 20th	Day	41% 8% 14% 22% 14% 1	2676
	21st to end	Day	35% 10% 19% 27% 9% 1	2700
July	1st to 10th	Day	26% 9% 16% 32% 16% 1	2626
	11th to 20th	Day	31% 9% 15% 27% 16% 2	2462
	21st to end	Day	28% 9% 16% 29% 17% 1	2591
August	1st to 10th	Day	34% 10% 14% 29% 10% 3	2327
	11th to 20th	Day	38% 7% 15% 29% 11%	2301
	21st to end	Day	32% 6% 16% 29% 15% 1	2484
September	1st to 10th	Day	35% 7% 14% 34% 10%	2160
	11th to 20th	Day	38% 7% 18% 30% 7%	2132
	21st to end	Day	42% 6% 13% 32% 7%	1895
October	1st to 10th	Day	46% 7% 13% 25% 9% 1	1800
	11th to 20th	Day	49% 6% 13% 21% 10% 1	1800
	21st to end	Day	52% 5% 12% 23% 8%	1936
November	1st to 10th	Day	52% 7% 11% 19% 10% 1	1523
	11th to 20th	Day	61% 5% 13% 14% 6% 1	1520
	21st to end	Day	53% 6% 16% 18% 5% 2	1520
December	1st to 10th	Day	62% 5% 14% 14% 5%	1520
	11th to 20th	Day	59% 7% 14% 16% 4	1915
	21st to end	Day	69% 5% 8% 11% 7%	2783
January	1st to 10th	Night	50% 5% 12% 22% 10% 1	2648
	11th to 20th	Night	54% 7% 15% 16% 8% 1	2561
	21st to end	Night	58% 6% 10% 16% 8% 1	2596
February	1st to 10th	Night	46% 6% 13% 23% 11% 1	2340
	11th to 20th	Night	44% 7% 13% 24% 10% 2	2274
	21st to end	Night	49% 6% 10% 22% 12% 1	1888
March	1st to 10th	Night	49% 6% 14% 20% 9% 1	2048
	11th to 20th	Night	44% 4 13% 23% 15%	1980
	21st to end	Night	49% 6% 13% 22% 10% 1	2155
April	1st to 10th	Night	48% 6% 9% 19% 16% 2	1800
	11th to 20th	Night	52% 5% 7% 21% 15% 2	1733
	21st to end	Night	50% 6% 9% 20% 13% 2	1620
May	1st to 10th	Night	45% 6% 14% 22% 13%	1494
	11th to 20th	Night	40% 7% 14% 23% 14% 3	1417
	21st to end	Night	37% 8% 15% 23% 15% 2	1552
June	1st to 10th	Night	36% 7% 16% 28% 11% 3	1440
	11th to 20th	Night	36% 7% 15% 24% 17% 2	1278
	21st to end	Night	31% 8% 16% 30% 12% 3	1260
July	1st to 10th	Night	21% 8% 19% 34% 17% 1	1225
	11th to 20th	Night	27% 8% 13% 31% 16% 4	1371
	21st to end	Night	21% 6% 18% 33% 18% 4	1487
August	1st to 10th	Night	27% 8% 15% 34% 12% 5%	1584
	11th to 20th	Night	30% 8% 16% 30% 15% 1	1600
	21st to end	Night	31% 7% 12% 31% 17% 3	1870
September	1st to 10th	Night	28% 7% 15% 34% 15% 1	1800
	11th to 20th	Night	31% 6% 17% 32% 14%	1826
	21st to end	Night	36% 6% 14% 33% 11%	2047
October	1st to 10th	Night	40% 5% 12% 30% 12% 1	2160
	11th to 20th	Night	45% 6% 13% 23% 12% 1	2160
	21st to end	Night	51% 5% 12% 22% 10% 1	2419
November	1st to 10th	Night	48% 6% 12% 23% 9% 2	2554
	11th to 20th	Night	56% 5% 14% 15% 9%	2660
	21st to end	Night	48% 8% 18% 20% 6% 1	2660
December	1st to 10th	Night	56% 7% 14% 17% 5% 1	2660
	11th to 20th	Night	57% 7% 12% 16% 5% 2	3281
	21st to end	Night	65% 5% 10% 15% 5%	4884

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	16% 11% 33% 27% 10% 3	270
	11th to 20th	Day	17% 11% 34% 32% 6%	248
	21st to end	Day	16% 7% 39% 22% 14% 1	264
February	1st to 10th	Day	17% 15% 44% 20% 5%	240
	11th to 20th	Day	13% 20% 40% 19% 6% 2	240
	21st to end	Day	19% 9% 41% 26% 5%	198
March	1st to 10th	Day	17% 13% 38% 23% 7% 2	240
	11th to 20th	Day	18% 9% 37% 23% 11% 2	240
	21st to end	Day	26% 12% 27% 22% 11% 2	286
April	1st to 10th	Day	21% 14% 32% 26% 6% 1	420
	11th to 20th	Day	28% 10% 28% 25% 9% 1	450
	21st to end	Day	26% 8% 31% 23% 10% 3	600
May	1st to 10th	Day	20% 10% 30% 28% 9% 2	603
	11th to 20th	Day	19% 13% 26% 27% 11% 4	625
	21st to end	Day	17% 7% 26% 29% 16% 4	679
June	1st to 10th	Day	12% 6% 27% 33% 18% 5%	630
	11th to 20th	Day	12% 8% 35% 31% 13% 2	630
	21st to end	Day	11% 6% 29% 31% 15% 8%	630
July	1st to 10th	Day	8% 4 22% 33% 23% 10%	621
	11th to 20th	Day	10% 6% 26% 30% 20% 8%	618
	21st to end	Day	8% 5% 27% 33% 21% 7%	684
August	1st to 10th	Day	10% 4 21% 36% 23% 5%	626
	11th to 20th	Day	14% 7% 20% 29% 25% 6%	615
	21st to end	Day	12% 8% 22% 31% 22% 4	603
September	1st to 10th	Day	11% 8% 29% 31% 17% 4	450
	11th to 20th	Day	11% 6% 28% 32% 21% 3	422
	21st to end	Day	21% 15% 27% 21% 11% 5%	270
October	1st to 10th	Day	19% 7% 30% 24% 12% 7%	270
	11th to 20th	Day	16% 18% 33% 27% 6%	270
	21st to end	Day	25% 12% 39% 17% 6%	297
November	1st to 10th	Day	20% 12% 35% 25% 8% 1	270
	11th to 20th	Day	16% 16% 41% 20% 6%	270
	21st to end	Day	21% 15% 37% 24% 3	270
December	1st to 10th	Day	16% 13% 39% 22% 10%	270
	11th to 20th	Day	19% 15% 36% 25% 4	270
	21st to end	Day	31% 10% 32% 24% 2 1	297
January	1st to 10th	Night	13% 10% 37% 31% 9% 1	950
	11th to 20th	Night	15% 8% 37% 30% 8% 1	915
	21st to end	Night	16% 10% 37% 29% 8% 1	990
February	1st to 10th	Night	11% 9% 40% 30% 9% 1	900
	11th to 20th	Night	11% 12% 41% 26% 9% 1	879
	21st to end	Night	15% 11% 36% 28% 9% 1	704
March	1st to 10th	Night	16% 12% 36% 26% 9% 1	608
	11th to 20th	Night	17% 9% 40% 27% 7%	540
	21st to end	Night	21% 11% 27% 29% 10% 3	594
April	1st to 10th	Night	21% 11% 36% 26% 6%	540
	11th to 20th	Night	26% 8% 29% 29% 8% 1	533
	21st to end	Night	24% 6% 30% 29% 10% 1	540
May	1st to 10th	Night	19% 8% 34% 31% 8% 1	540
	11th to 20th	Night	17% 7% 33% 31% 11% 2	531
	21st to end	Night	16% 5% 27% 36% 16%	584
June	1st to 10th	Night	12% 4 25% 41% 17% 1	540
	11th to 20th	Night	12% 4 32% 39% 12%	540
	21st to end	Night	11% 5% 21% 42% 20% 1	540
July	1st to 10th	Night	4 2 22% 44% 26% 2	525
	11th to 20th	Night	8% 4 25% 39% 22% 2	522
	21st to end	Night	5% 3 21% 47% 21% 3	591
August	1st to 10th	Night	7% 3 15% 53% 20% 2	537
	11th to 20th	Night	14% 3 20% 35% 26% 3	534
	21st to end	Night	12% 4 21% 37% 24% 2	594
September	1st to 10th	Night	11% 4 23% 39% 20% 3	540
	11th to 20th	Night	11% 4 28% 35% 19% 2	540
	21st to end	Night	17% 9% 31% 29% 14% 1	607
October	1st to 10th	Night	19% 7% 29% 30% 13% 1	720
	11th to 20th	Night	21% 11% 32% 30% 6% 1	720
	21st to end	Night	23% 11% 29% 30% 6%	792
November	1st to 10th	Night	19% 11% 29% 32% 9%	888
	11th to 20th	Night	19% 12% 32% 28% 9% 1	950
	21st to end	Night	16% 13% 37% 26% 7%	950
December	1st to 10th	Night	16% 11% 34% 31% 8% 1	950
	11th to 20th	Night	20% 10% 35% 28% 7% 1	950
	21st to end	Night	25% 10% 33% 25% 6% 1	1045

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