Gimli
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gimli clear sky chart from 2005-11-06 to 2024-11-05.

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	11% 9% 3 8% 6% 5% 5% 4 6% 8% 35%	105605
	Night	10% 10% 4 9% 6% 5% 5% 4 6% 7% 35%	102021
Transparency	Day	45% 7% 17% 24% 7%	105346
	Night	47% 7% 14% 23% 8% 1	101927
Seeing	Day	13% 4 20% 34% 23% 6%	16284
	Night	15% 4 24% 37% 18% 3	26199

By Month

Percentage Cloud Cover NW (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% 16% 6% 10% 8% 8% 9% 5% 7% 5% 20%	2219
	11th to 20th	Day	5% 10% 5% 21% 12% 10% 7% 4 8% 7% 12%	2199
	21st to end	Day	7% 17% 7% 15% 7% 6% 6% 5% 6% 7% 17%	2712
February	1st to 10th	Day	9% 11% 6% 12% 8% 7% 8% 5% 8% 6% 19%	1609
	11th to 20th	Day	7% 10% 4 10% 6% 7% 6% 5% 7% 9% 26%	1664
	21st to end	Day	5% 13% 4 10% 8% 6% 8% 5% 7% 8% 26%	1468
March	1st to 10th	Day	10% 10% 5% 10% 7% 6% 6% 5% 7% 8% 25%	3210
	11th to 20th	Day	7% 11% 5% 14% 9% 7% 6% 4 6% 6% 25%	3478
	21st to end	Day	7% 11% 5% 11% 7% 6% 7% 4 5% 6% 30%	3814
April	1st to 10th	Day	10% 10% 3 9% 5% 5% 4 4 6% 7% 37%	2328
	11th to 20th	Day	12% 9% 4 7% 6% 4 6% 5% 5% 7% 36%	2442
	21st to end	Day	13% 7% 3 7% 6% 5% 5% 4 6% 7% 37%	2470
May	1st to 10th	Day	15% 8% 3 7% 4 4 4 4 5% 8% 38%	4311
	11th to 20th	Day	19% 9% 3 8% 4 5% 4 3 6% 6% 34%	4664
	21st to end	Day	20% 7% 3 7% 5% 4 4 4 5% 7% 36%	5173
June	1st to 10th	Day	15% 7% 2 7% 5% 5% 4 4 5% 8% 36%	2850
	11th to 20th	Day	14% 7% 3 7% 5% 5% 5% 4 6% 8% 36%	2850
	21st to end	Day	12% 5% 3 7% 6% 5% 5% 4 7% 9% 37%	2850
July	1st to 10th	Day	10% 5% 2 6% 5% 5% 6% 5% 8% 9% 38%	4750
	11th to 20th	Day	8% 4 2 4 3 4 4 4 6% 10% 50%	4750
	21st to end	Day	5% 4 2 5% 4 4 4 4 6% 10% 51%	5150
August	1st to 10th	Day	8% 4 2 6% 5% 5% 5% 4 7% 9% 45%	4314
	11th to 20th	Day	10% 5% 2 6% 5% 4 5% 4 5% 8% 47%	4041
	21st to end	Day	12% 7% 2 6% 4 4 4 4 6% 8% 44%	4532
September	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 6% 7% 48%	2379
	11th to 20th	Day	13% 8% 3 8% 5% 6% 4 3 6% 8% 37%	2090
	21st to end	Day	15% 7% 2 6% 5% 4 4 3 6% 9% 39%	2090
October	1st to 10th	Day	13% 9% 3 6% 4 5% 5% 4 5% 7% 40%	3200
	11th to 20th	Day	9% 10% 3 8% 5% 5% 5% 4 7% 8% 36%	3061
	21st to end	Day	13% 12% 4 9% 5% 5% 5% 3 6% 9% 30%	3075
November	1st to 10th	Day	16% 15% 4 12% 6% 4 4 3 5% 5% 26%	1519
	11th to 20th	Day	10% 16% 5% 12% 6% 6% 5% 5% 5% 5% 26%	1520
	21st to end	Day	12% 16% 5% 10% 7% 5% 5% 4 5% 7% 24%	1372
December	1st to 10th	Day	8% 14% 5% 14% 10% 8% 7% 4 7% 7% 16%	1330
	11th to 20th	Day	9% 15% 6% 13% 8% 5% 5% 5% 6% 7% 21%	1679
	21st to end	Day	8% 12% 4 11% 6% 6% 6% 5% 6% 7% 28%	2442
January	1st to 10th	Night	5% 13% 5% 13% 8% 9% 8% 5% 6% 7% 21%	4737
	11th to 20th	Night	5% 13% 6% 16% 12% 10% 8% 5% 5% 5% 14%	4709
	21st to end	Night	8% 16% 7% 14% 7% 6% 5% 4 6% 6% 20%	4940
February	1st to 10th	Night	8% 12% 5% 11% 7% 7% 6% 5% 6% 6% 26%	2570
	11th to 20th	Night	6% 10% 5% 9% 5% 5% 7% 5% 7% 8% 33%	2403
	21st to end	Night	5% 12% 3 10% 5% 6% 6% 5% 5% 8% 34%	2003
March	1st to 10th	Night	11% 11% 3 9% 5% 6% 5% 5% 7% 8% 29%	3650
	11th to 20th	Night	5% 8% 3 7% 5% 5% 6% 5% 6% 8% 43%	3480
	21st to end	Night	9% 13% 4 9% 5% 5% 4 3 5% 7% 37%	3817
April	1st to 10th	Night	12% 6% 2 6% 4 4 5% 4 6% 9% 42%	1846
	11th to 20th	Night	13% 10% 4 7% 6% 4 5% 4 5% 6% 37%	1689
	21st to end	Night	10% 8% 3 7% 6% 6% 6% 4 6% 6% 38%	1710
May	1st to 10th	Night	18% 8% 3 7% 4 5% 4 4 5% 6% 36%	2658
	11th to 20th	Night	17% 6% 2 7% 4 4 4 4 5% 7% 39%	2241
	21st to end	Night	17% 7% 2 6% 4 3 4 3 6% 7% 41%	2414
June	1st to 10th	Night	15% 7% 2 6% 5% 4 4 4 6% 7% 39%	1330
	11th to 20th	Night	16% 6% 2 5% 5% 4 5% 3 6% 9% 41%	1330
	21st to end	Night	12% 4 2 6% 4 5% 5% 5% 8% 9% 40%	1330
July	1st to 10th	Night	10% 3 2 5% 2 4 4 4 6% 10% 51%	2220
	11th to 20th	Night	7% 3 1 4 4 4 4 3 5% 10% 55%	2220
	21st to end	Night	4 3 2 5% 4 4 4 5% 7% 9% 54%	2414
August	1st to 10th	Night	8% 4 1 5% 4 4 5% 5% 7% 9% 48%	2609
	11th to 20th	Night	8% 3 1 4 3 4 4 4 7% 11% 51%	2798
	21st to end	Night	9% 5% 2 5% 4 5% 4 3 5% 8% 48%	3135
September	1st to 10th	Night	11% 5% 3 5% 4 3 3 4 6% 7% 50%	1800
	11th to 20th	Night	13% 5% 3 7% 4 4 3 3 6% 8% 45%	2090
	21st to end	Night	14% 7% 2 6% 4 4 4 3 5% 8% 41%	2090
October	1st to 10th	Night	15% 8% 2 5% 3 3 4 3 5% 8% 44%	3727
	11th to 20th	Night	10% 8% 3 8% 5% 5% 4 3 6% 8% 39%	3859
	21st to end	Night	9% 9% 3 9% 6% 6% 5% 4 6% 7% 37%	4482
November	1st to 10th	Night	14% 15% 3 9% 5% 5% 6% 4 6% 6% 27%	2660
	11th to 20th	Night	10% 15% 6% 13% 7% 6% 5% 3 5% 6% 25%	2660
	21st to end	Night	13% 14% 6% 13% 7% 5% 5% 3 5% 6% 23%	2807
December	1st to 10th	Night	7% 11% 5% 13% 10% 8% 6% 4 5% 7% 23%	2850
	11th to 20th	Night	8% 17% 6% 10% 7% 5% 5% 5% 6% 6% 24%	3518
	21st to end	Night	8% 10% 4 13% 8% 6% 5% 4 6% 7% 28%	5225

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	63% 7% 12% 14% 3	2219
	11th to 20th	Day	69% 5% 10% 13% 3	2220
	21st to end	Day	64% 9% 9% 13% 5%	2712
February	1st to 10th	Day	59% 6% 14% 13% 8% 1	1609
	11th to 20th	Day	50% 6% 15% 21% 8%	1673
	21st to end	Day	52% 8% 12% 20% 8%	1468
March	1st to 10th	Day	53% 7% 14% 20% 5%	3210
	11th to 20th	Day	50% 8% 15% 20% 7%	3480
	21st to end	Day	47% 7% 15% 22% 7% 1	3814
April	1st to 10th	Day	44% 6% 13% 25% 11% 1	2328
	11th to 20th	Day	44% 5% 14% 22% 14% 2	2442
	21st to end	Day	43% 7% 15% 26% 8% 2	2470
May	1st to 10th	Day	41% 5% 15% 28% 11% 1	4311
	11th to 20th	Day	49% 7% 10% 21% 12% 2	4668
	21st to end	Day	46% 8% 12% 23% 10% 1	5173
June	1st to 10th	Day	43% 7% 15% 23% 11% 1	2850
	11th to 20th	Day	42% 8% 15% 22% 12% 1	2850
	21st to end	Day	40% 9% 19% 23% 8%	2850
July	1st to 10th	Day	35% 10% 24% 24% 7%	4676
	11th to 20th	Day	27% 7% 24% 36% 6%	4669
	21st to end	Day	27% 7% 24% 35% 7%	4988
August	1st to 10th	Day	31% 8% 21% 31% 9%	4297
	11th to 20th	Day	34% 7% 23% 31% 5%	4080
	21st to end	Day	36% 7% 25% 27% 5%	4531
September	1st to 10th	Day	34% 8% 19% 31% 8% 1	2379
	11th to 20th	Day	45% 7% 19% 25% 4	2090
	21st to end	Day	41% 7% 18% 27% 7%	2090
October	1st to 10th	Day	43% 6% 16% 28% 7%	3200
	11th to 20th	Day	43% 8% 13% 26% 9%	3061
	21st to end	Day	50% 7% 19% 20% 3	3075
November	1st to 10th	Day	61% 7% 11% 17% 4 1	1519
	11th to 20th	Day	62% 11% 10% 14% 3	1520
	21st to end	Day	61% 10% 15% 12% 2	1372
December	1st to 10th	Day	66% 8% 12% 11% 3	1330
	11th to 20th	Day	62% 6% 15% 12% 4	1680
	21st to end	Day	51% 12% 11% 19% 7%	2442
January	1st to 10th	Night	60% 10% 11% 15% 5%	4737
	11th to 20th	Night	70% 6% 8% 13% 3	4750
	21st to end	Night	63% 7% 12% 14% 4	4940
February	1st to 10th	Night	56% 7% 12% 15% 9% 1	2570
	11th to 20th	Night	45% 7% 16% 21% 10%	2404
	21st to end	Night	49% 6% 11% 22% 11%	2003
March	1st to 10th	Night	51% 7% 11% 23% 9% 1	3650
	11th to 20th	Night	36% 8% 14% 29% 13% 1	3480
	21st to end	Night	47% 5% 11% 26% 10% 1	3817
April	1st to 10th	Night	39% 6% 11% 25% 17% 3	1846
	11th to 20th	Night	47% 5% 9% 21% 15% 3	1689
	21st to end	Night	43% 7% 11% 24% 13% 2	1710
May	1st to 10th	Night	47% 6% 9% 25% 13%	2658
	11th to 20th	Night	43% 6% 12% 28% 9% 2	2241
	21st to end	Night	42% 8% 10% 27% 11% 1	2414
June	1st to 10th	Night	42% 8% 14% 24% 12% 1	1330
	11th to 20th	Night	39% 7% 17% 21% 14% 2	1330
	21st to end	Night	35% 9% 22% 25% 9% 1	1330
July	1st to 10th	Night	28% 9% 20% 34% 9% 1	2185
	11th to 20th	Night	27% 6% 19% 38% 8% 1	2178
	21st to end	Night	25% 8% 22% 35% 9% 1	2337
August	1st to 10th	Night	31% 8% 18% 31% 12%	2602
	11th to 20th	Night	26% 8% 27% 32% 7%	2825
	21st to end	Night	32% 8% 21% 31% 8%	3135
September	1st to 10th	Night	33% 8% 17% 31% 11%	1800
	11th to 20th	Night	39% 8% 19% 25% 9% 1	2090
	21st to end	Night	42% 7% 15% 27% 9% 1	2090
October	1st to 10th	Night	40% 5% 13% 29% 13%	3727
	11th to 20th	Night	43% 7% 13% 28% 10%	3859
	21st to end	Night	46% 7% 17% 26% 4	4482
November	1st to 10th	Night	60% 7% 13% 14% 5% 1	2660
	11th to 20th	Night	61% 9% 13% 11% 5%	2660
	21st to end	Night	63% 8% 14% 11% 4	2807
December	1st to 10th	Night	62% 8% 16% 11% 3	2850
	11th to 20th	Night	58% 8% 14% 14% 6%	3516
	21st to end	Night	53% 9% 11% 17% 9% 1	5225

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	10% 3 26% 37% 20% 4	270
	11th to 20th	Day	8% 5% 19% 43% 22% 3	270
	21st to end	Day	16% 3 20% 36% 21% 5%	297
February	1st to 10th	Day	13% 3 25% 38% 18% 3	270
	11th to 20th	Day	10% 3 29% 33% 19% 7%	270
	21st to end	Day	5% 3 23% 42% 25% 3	225
March	1st to 10th	Day	12% 4 21% 31% 25% 7%	270
	11th to 20th	Day	10% 4 22% 37% 21% 5%	270
	21st to end	Day	11% 3 19% 33% 28% 6%	297
April	1st to 10th	Day	12% 3 19% 38% 21% 6%	508
	11th to 20th	Day	15% 4 20% 33% 24% 4	640
	21st to end	Day	14% 3 18% 36% 24% 4	650
May	1st to 10th	Day	12% 4 19% 36% 25% 4	653
	11th to 20th	Day	15% 6% 15% 31% 26% 6%	675
	21st to end	Day	19% 4 15% 28% 28% 7%	734
June	1st to 10th	Day	16% 5% 18% 31% 22% 8%	680
	11th to 20th	Day	14% 6% 21% 36% 20% 4	680
	21st to end	Day	12% 4 13% 35% 26% 10%	680
July	1st to 10th	Day	9% 3 17% 31% 30% 11%	671
	11th to 20th	Day	11% 3 18% 31% 26% 10%	668
	21st to end	Day	6% 4 16% 34% 31% 11%	739
August	1st to 10th	Day	8% 3 18% 33% 26% 12%	676
	11th to 20th	Day	10% 4 14% 31% 30% 11%	665
	21st to end	Day	14% 4 17% 32% 25% 8%	748
September	1st to 10th	Day	10% 4 23% 36% 23% 4	589
	11th to 20th	Day	15% 7% 23% 34% 17% 4	300
	21st to end	Day	19% 5% 20% 34% 20% 2	300
October	1st to 10th	Day	21% 6% 20% 33% 16% 4	300
	11th to 20th	Day	13% 9% 25% 38% 13% 2	300
	21st to end	Day	20% 7% 27% 29% 13% 3	330
November	1st to 10th	Day	22% 3 22% 33% 17% 3	282
	11th to 20th	Day	18% 4 34% 29% 13% 2	270
	21st to end	Day	21% 7% 26% 36% 9%	270
December	1st to 10th	Day	15% 3 24% 35% 19% 4	270
	11th to 20th	Day	16% 7% 27% 36% 12% 2	270
	21st to end	Day	10% 3 22% 36% 24% 5%	297
January	1st to 10th	Night	13% 4 27% 36% 18% 3	950
	11th to 20th	Night	13% 5% 25% 41% 15% 2	950
	21st to end	Night	15% 3 23% 40% 16% 2	1045
February	1st to 10th	Night	13% 3 24% 40% 18% 2	950
	11th to 20th	Night	10% 3 25% 37% 21% 4	929
	21st to end	Night	10% 3 26% 38% 21% 2	747
March	1st to 10th	Night	15% 3 21% 38% 21% 3	715
	11th to 20th	Night	12% 2 29% 40% 14% 3	570
	21st to end	Night	17% 4 21% 36% 17% 5%	627
April	1st to 10th	Night	14% 2 24% 42% 16% 3	570
	11th to 20th	Night	16% 4 20% 38% 20% 2	563
	21st to end	Night	13% 2 22% 44% 16% 3	570
May	1st to 10th	Night	20% 3 19% 39% 16% 2	570
	11th to 20th	Night	16% 5% 16% 38% 21% 4	561
	21st to end	Night	18% 3 19% 35% 22% 2	617
June	1st to 10th	Night	17% 3 20% 32% 25% 3	570
	11th to 20th	Night	18% 4 18% 37% 21% 3	570
	21st to end	Night	13% 4 13% 38% 28% 4	570
July	1st to 10th	Night	9% 2 15% 40% 29% 5%	555
	11th to 20th	Night	9% 4 18% 38% 26% 5%	552
	21st to end	Night	8% 3 16% 38% 29% 7%	624
August	1st to 10th	Night	10% 2 16% 41% 26% 5%	567
	11th to 20th	Night	9% 3 14% 39% 28% 7%	564
	21st to end	Night	12% 4 18% 37% 25% 3	627
September	1st to 10th	Night	14% 4 24% 37% 18% 4	570
	11th to 20th	Night	18% 5% 21% 40% 14% 2	570
	21st to end	Night	17% 5% 28% 34% 15% 1	570
October	1st to 10th	Night	23% 6% 28% 31% 11% 1	713
	11th to 20th	Night	20% 7% 28% 32% 12% 1	803
	21st to end	Night	21% 8% 27% 33% 10% 1	1045
November	1st to 10th	Night	22% 5% 31% 27% 14% 1	950
	11th to 20th	Night	17% 7% 33% 31% 8% 3	950
	21st to end	Night	20% 6% 33% 32% 8% 1	950
December	1st to 10th	Night	11% 3 27% 40% 16% 3	950
	11th to 20th	Night	15% 5% 30% 36% 12% 2	950
	21st to end	Night	18% 4 27% 32% 17% 2	1045

Page generated at 2024-11-03 01:11:15. Version ac07

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