Glennifer Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Glennifer Lake 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	9% 9% 3 8% 5% 5% 5% 4 7% 8% 36%	105668
	Night	7% 10% 4 9% 6% 5% 5% 5% 7% 8% 35%	101943
Transparency	Day	42% 9% 16% 22% 9% 1	105413
	Night	44% 9% 15% 21% 9% 2	101844
Seeing	Day	12% 6% 25% 32% 19% 6%	15384
	Night	12% 5% 29% 38% 15% 2	24358

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	3 12% 7% 13% 6% 4 4 3 7% 7% 33%	2219
	11th to 20th	Day	4 9% 4 10% 6% 7% 7% 4 7% 9% 33%	2199
	21st to end	Day	4 9% 3 8% 5% 7% 5% 4 6% 9% 38%	2776
February	1st to 10th	Day	6% 14% 5% 11% 5% 7% 6% 4 6% 8% 28%	1520
	11th to 20th	Day	5% 13% 4 13% 7% 5% 7% 6% 6% 7% 26%	1617
	21st to end	Day	3 11% 6% 13% 8% 6% 6% 5% 7% 7% 28%	1522
March	1st to 10th	Day	3 11% 5% 15% 8% 6% 6% 4 5% 7% 30%	3138
	11th to 20th	Day	5% 10% 3 6% 4 4 5% 4 7% 10% 41%	3425
	21st to end	Day	9% 21% 6% 11% 5% 5% 5% 3 5% 6% 25%	3912
April	1st to 10th	Day	8% 14% 4 9% 8% 5% 5% 5% 7% 8% 28%	2333
	11th to 20th	Day	12% 14% 4 10% 6% 5% 5% 4 6% 7% 27%	2440
	21st to end	Day	11% 12% 4 9% 6% 5% 4 4 7% 8% 31%	2470
May	1st to 10th	Day	18% 13% 3 8% 5% 5% 5% 4 5% 6% 28%	4462
	11th to 20th	Day	9% 11% 4 10% 6% 6% 6% 5% 7% 8% 30%	4694
	21st to end	Day	17% 10% 4 9% 6% 6% 6% 5% 7% 7% 24%	5161
June	1st to 10th	Day	17% 7% 3 7% 6% 6% 6% 6% 7% 7% 28%	2850
	11th to 20th	Day	19% 9% 4 8% 7% 6% 5% 5% 6% 7% 25%	2850
	21st to end	Day	9% 6% 2 7% 5% 5% 6% 6% 8% 10% 35%	2850
July	1st to 10th	Day	8% 5% 2 5% 4 4 5% 5% 7% 8% 48%	4740
	11th to 20th	Day	8% 4 2 4 3 4 5% 5% 8% 10% 47%	4740
	21st to end	Day	7% 4 2 5% 4 4 5% 4 7% 11% 48%	5080
August	1st to 10th	Day	9% 6% 2 7% 4 4 5% 5% 7% 10% 41%	4401
	11th to 20th	Day	7% 5% 2 6% 4 5% 6% 5% 9% 11% 40%	4127
	21st to end	Day	10% 5% 2 5% 4 4 5% 4 7% 8% 46%	4521
September	1st to 10th	Day	12% 6% 2 6% 3 4 4 4 6% 7% 45%	2370
	11th to 20th	Day	15% 9% 2 5% 3 3 4 3 4 7% 44%	2092
	21st to end	Day	9% 7% 3 7% 4 4 5% 4 6% 8% 42%	2090
October	1st to 10th	Day	7% 7% 3 7% 5% 5% 5% 5% 7% 10% 40%	3346
	11th to 20th	Day	8% 6% 3 8% 5% 6% 6% 5% 7% 9% 37%	2873
	21st to end	Day	7% 8% 4 8% 6% 5% 5% 4 6% 6% 40%	3101
November	1st to 10th	Day	7% 16% 5% 11% 7% 5% 5% 4 5% 7% 30%	1569
	11th to 20th	Day	6% 14% 4 10% 7% 4 5% 4 5% 7% 35%	1396
	21st to end	Day	5% 12% 4 10% 6% 5% 5% 4 7% 8% 33%	1330
December	1st to 10th	Day	6% 13% 4 13% 7% 7% 5% 5% 4 7% 29%	1330
	11th to 20th	Day	3 10% 5% 13% 7% 6% 6% 5% 6% 9% 29%	1682
	21st to end	Day	3 9% 4 10% 6% 5% 6% 4 6% 8% 41%	2442
January	1st to 10th	Night	3 13% 6% 14% 7% 7% 7% 5% 6% 7% 26%	4726
	11th to 20th	Night	3 9% 5% 13% 7% 5% 6% 6% 6% 8% 32%	4699
	21st to end	Night	4 11% 5% 10% 6% 5% 6% 5% 7% 8% 33%	4895
February	1st to 10th	Night	6% 13% 5% 13% 7% 6% 6% 4 6% 7% 27%	2660
	11th to 20th	Night	4 12% 6% 11% 8% 7% 6% 5% 6% 7% 27%	2449
	21st to end	Night	3 10% 5% 11% 7% 7% 5% 4 6% 8% 33%	1932
March	1st to 10th	Night	3 9% 4 16% 8% 7% 7% 5% 7% 8% 26%	3736
	11th to 20th	Night	6% 9% 3 7% 6% 5% 7% 6% 8% 9% 36%	3553
	21st to end	Night	7% 18% 7% 14% 7% 6% 5% 5% 5% 6% 20%	3738
April	1st to 10th	Night	8% 13% 4 8% 6% 6% 6% 5% 7% 8% 30%	1846
	11th to 20th	Night	10% 13% 5% 12% 6% 4 5% 3 6% 7% 28%	1691
	21st to end	Night	12% 10% 3 10% 5% 5% 5% 5% 8% 7% 31%	1710
May	1st to 10th	Night	22% 13% 4 7% 5% 3 3 3 5% 5% 29%	2496
	11th to 20th	Night	11% 9% 3 7% 6% 5% 5% 5% 8% 9% 32%	2199
	21st to end	Night	18% 10% 4 9% 6% 6% 6% 5% 7% 7% 21%	2414
June	1st to 10th	Night	15% 11% 4 8% 5% 5% 6% 4 7% 7% 29%	1330
	11th to 20th	Night	17% 9% 4 8% 7% 6% 6% 5% 6% 8% 24%	1330
	21st to end	Night	10% 7% 2 7% 5% 4 5% 6% 8% 9% 38%	1330
July	1st to 10th	Night	9% 6% 3 8% 5% 6% 5% 4 6% 7% 41%	2220
	11th to 20th	Night	6% 3 2 5% 3 4 6% 5% 9% 11% 48%	2220
	21st to end	Night	7% 5% 2 5% 4 5% 4 4 6% 10% 48%	2469
August	1st to 10th	Night	11% 8% 2 7% 4 4 5% 3 5% 7% 44%	2529
	11th to 20th	Night	8% 6% 3 7% 5% 4 5% 5% 8% 12% 38%	2707
	21st to end	Night	10% 6% 2 6% 4 4 4 4 7% 8% 45%	3146
September	1st to 10th	Night	10% 6% 2 7% 3 3 5% 3 7% 7% 46%	1806
	11th to 20th	Night	16% 7% 3 6% 3 4 5% 3 5% 8% 41%	2088
	21st to end	Night	9% 7% 2 6% 3 4 6% 4 7% 7% 44%	2090
October	1st to 10th	Night	7% 6% 3 6% 5% 4 5% 5% 6% 9% 45%	3628
	11th to 20th	Night	6% 8% 3 8% 4 4 5% 4 7% 9% 41%	4053
	21st to end	Night	5% 9% 3 8% 6% 5% 5% 5% 7% 8% 40%	4457
November	1st to 10th	Night	9% 14% 4 9% 5% 4 6% 4 6% 7% 32%	2589
	11th to 20th	Night	5% 12% 4 10% 7% 5% 5% 4 7% 8% 32%	2783
	21st to end	Night	4 12% 4 10% 6% 5% 5% 4 7% 9% 34%	2850
December	1st to 10th	Night	6% 13% 4 9% 7% 7% 5% 3 5% 7% 34%	2850
	11th to 20th	Night	3 10% 4 12% 8% 7% 7% 5% 7% 8% 29%	3510
	21st to end	Night	2 10% 3 8% 5% 4 5% 4 6% 7% 44%	5214

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	47% 8% 12% 21% 11% 1	2219
	11th to 20th	Day	44% 9% 10% 15% 18% 4	2220
	21st to end	Day	40% 9% 16% 27% 8% 1	2776
February	1st to 10th	Day	51% 9% 13% 17% 9% 2	1520
	11th to 20th	Day	51% 11% 14% 14% 8% 2	1626
	21st to end	Day	51% 9% 13% 17% 10% 1	1522
March	1st to 10th	Day	50% 9% 16% 15% 10%	3138
	11th to 20th	Day	34% 10% 19% 24% 13% 1	3426
	21st to end	Day	58% 9% 12% 15% 6%	3912
April	1st to 10th	Day	48% 12% 18% 16% 6%	2333
	11th to 20th	Day	52% 9% 12% 19% 8%	2440
	21st to end	Day	48% 9% 15% 20% 6% 1	2470
May	1st to 10th	Day	52% 9% 12% 22% 5%	4462
	11th to 20th	Day	44% 14% 15% 19% 9%	4698
	21st to end	Day	50% 14% 16% 14% 5% 1	5162
June	1st to 10th	Day	49% 11% 16% 18% 5% 1	2850
	11th to 20th	Day	54% 11% 14% 16% 5% 1	2850
	21st to end	Day	39% 13% 20% 22% 6% 1	2850
July	1st to 10th	Day	30% 9% 17% 29% 12% 3	4666
	11th to 20th	Day	29% 9% 20% 34% 8% 1	4659
	21st to end	Day	29% 8% 17% 28% 16% 3	4919
August	1st to 10th	Day	36% 10% 18% 29% 8%	4384
	11th to 20th	Day	32% 11% 24% 26% 7% 1	4168
	21st to end	Day	33% 8% 22% 29% 7% 1	4520
September	1st to 10th	Day	35% 8% 21% 22% 11% 3	2370
	11th to 20th	Day	40% 7% 15% 27% 10% 1	2092
	21st to end	Day	37% 9% 16% 24% 11% 3	2090
October	1st to 10th	Day	38% 7% 21% 29% 6% 1	3346
	11th to 20th	Day	41% 7% 19% 20% 11% 2	2873
	21st to end	Day	43% 6% 11% 32% 8% 1	3101
November	1st to 10th	Day	53% 8% 13% 17% 8% 2	1569
	11th to 20th	Day	47% 9% 13% 21% 10% 1	1396
	21st to end	Day	46% 9% 17% 18% 9% 2	1330
December	1st to 10th	Day	53% 7% 12% 17% 9% 2	1330
	11th to 20th	Day	47% 10% 18% 18% 5% 2	1684
	21st to end	Day	36% 9% 13% 20% 18% 4	2442
January	1st to 10th	Night	52% 10% 12% 16% 8% 2	4726
	11th to 20th	Night	47% 8% 11% 15% 14% 5%	4740
	21st to end	Night	42% 11% 15% 22% 9% 1	4895
February	1st to 10th	Night	54% 7% 11% 18% 9% 1	2660
	11th to 20th	Night	52% 7% 14% 16% 10% 1	2450
	21st to end	Night	46% 7% 13% 21% 12% 2	1932
March	1st to 10th	Night	49% 11% 12% 20% 8%	3736
	11th to 20th	Night	36% 14% 21% 17% 11% 1	3553
	21st to end	Night	60% 11% 11% 13% 4 1	3738
April	1st to 10th	Night	48% 10% 15% 18% 10%	1846
	11th to 20th	Night	52% 7% 14% 18% 8% 1	1691
	21st to end	Night	47% 9% 16% 20% 6% 1	1710
May	1st to 10th	Night	55% 7% 12% 20% 6%	2496
	11th to 20th	Night	39% 14% 16% 22% 9%	2199
	21st to end	Night	51% 15% 16% 13% 4 1	2414
June	1st to 10th	Night	49% 12% 13% 17% 7% 1	1330
	11th to 20th	Night	55% 11% 12% 16% 5% 2	1330
	21st to end	Night	38% 12% 20% 22% 7% 1	1330
July	1st to 10th	Night	40% 10% 14% 22% 12% 3	2185
	11th to 20th	Night	26% 10% 22% 31% 7% 4	2178
	21st to end	Night	30% 8% 17% 30% 14% 1	2391
August	1st to 10th	Night	38% 8% 17% 29% 7%	2521
	11th to 20th	Night	35% 10% 25% 25% 6% 1	2732
	21st to end	Night	34% 8% 21% 28% 8% 1	3146
September	1st to 10th	Night	33% 9% 18% 25% 12% 4	1806
	11th to 20th	Night	39% 9% 16% 23% 10% 3	2088
	21st to end	Night	35% 8% 17% 24% 13% 3	2090
October	1st to 10th	Night	34% 7% 19% 27% 13% 1	3628
	11th to 20th	Night	37% 7% 18% 28% 9% 1	4053
	21st to end	Night	40% 8% 14% 29% 8%	4457
November	1st to 10th	Night	49% 8% 12% 19% 10% 2	2589
	11th to 20th	Night	47% 8% 16% 17% 11% 1	2783
	21st to end	Night	44% 9% 18% 18% 7% 3	2850
December	1st to 10th	Night	49% 7% 12% 19% 10% 3	2850
	11th to 20th	Night	49% 10% 15% 19% 6% 1	3507
	21st to end	Night	36% 7% 14% 23% 15% 5%	5214

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	5% 4 25% 35% 22% 9%	180
	11th to 20th	Day	8% 2 31% 37% 16% 6%	180
	21st to end	Day	6% 7% 26% 32% 21% 8%	198
February	1st to 10th	Day	10% 9% 22% 37% 13% 8%	180
	11th to 20th	Day	12% 4 24% 40% 15% 4	247
	21st to end	Day	4 4 30% 35% 21% 6%	334
March	1st to 10th	Day	8% 6% 32% 34% 15% 5%	460
	11th to 20th	Day	7% 5% 29% 37% 16% 7%	460
	21st to end	Day	14% 7% 29% 29% 15% 6%	506
April	1st to 10th	Day	10% 10% 33% 30% 14% 3	460
	11th to 20th	Day	16% 8% 27% 29% 15% 5%	452
	21st to end	Day	16% 8% 27% 29% 16% 3	460
May	1st to 10th	Day	17% 8% 24% 28% 17% 5%	529
	11th to 20th	Day	11% 9% 22% 33% 20% 5%	675
	21st to end	Day	17% 6% 18% 31% 21% 7%	734
June	1st to 10th	Day	17% 6% 24% 36% 13% 3	680
	11th to 20th	Day	20% 7% 23% 30% 14% 5%	680
	21st to end	Day	11% 6% 23% 31% 21% 9%	680
July	1st to 10th	Day	13% 3 18% 32% 25% 9%	671
	11th to 20th	Day	13% 4 18% 34% 24% 7%	668
	21st to end	Day	7% 4 21% 32% 26% 9%	705
August	1st to 10th	Day	10% 3 23% 30% 23% 9%	487
	11th to 20th	Day	7% 5% 22% 32% 28% 6%	477
	21st to end	Day	12% 6% 21% 31% 24% 7%	539
September	1st to 10th	Day	16% 4 26% 29% 18% 7%	490
	11th to 20th	Day	20% 6% 21% 28% 19% 7%	490
	21st to end	Day	12% 10% 30% 29% 13% 6%	490
October	1st to 10th	Day	14% 8% 26% 27% 17% 8%	411
	11th to 20th	Day	12% 8% 29% 30% 16% 5%	300
	21st to end	Day	12% 10% 34% 29% 13% 3	330
November	1st to 10th	Day	17% 5% 23% 37% 13% 5%	282
	11th to 20th	Day	15% 6% 31% 33% 14% 1	211
	21st to end	Day	4 6% 31% 37% 12% 10%	180
December	1st to 10th	Day	11% 4 26% 32% 22% 4	180
	11th to 20th	Day	9% 6% 37% 31% 16% 3	180
	21st to end	Day	6% 5% 24% 31% 29% 6%	198
January	1st to 10th	Night	10% 7% 33% 35% 15% 1	950
	11th to 20th	Night	11% 5% 32% 38% 13% 1	950
	21st to end	Night	10% 9% 30% 38% 11% 2	856
February	1st to 10th	Night	10% 8% 27% 36% 16% 3	760
	11th to 20th	Night	8% 6% 32% 40% 14% 1	744
	21st to end	Night	6% 4 28% 36% 22% 4	628
March	1st to 10th	Night	9% 4 31% 39% 15% 3	760
	11th to 20th	Night	8% 5% 30% 41% 13% 2	760
	21st to end	Night	12% 4 29% 38% 14% 3	836
April	1st to 10th	Night	12% 5% 32% 36% 14% 1	706
	11th to 20th	Night	15% 5% 33% 35% 12%	563
	21st to end	Night	15% 8% 26% 37% 12% 1	570
May	1st to 10th	Night	18% 8% 25% 36% 12% 1	428
	11th to 20th	Night	11% 7% 27% 37% 17% 1	374
	21st to end	Night	21% 5% 19% 36% 18% 1	411
June	1st to 10th	Night	20% 4 25% 36% 13% 2	380
	11th to 20th	Night	21% 3 25% 35% 16%	380
	21st to end	Night	11% 2 22% 40% 23% 2	380
July	1st to 10th	Night	14% 3 14% 45% 24% 1	370
	11th to 20th	Night	11% 3 18% 47% 18% 2	368
	21st to end	Night	10% 2 17% 41% 29% 2	416
August	1st to 10th	Night	10% 3 18% 35% 32% 2	378
	11th to 20th	Night	12% 3 17% 42% 25% 2	496
	21st to end	Night	11% 3 21% 44% 21%	627
September	1st to 10th	Night	13% 3 21% 42% 18% 2	666
	11th to 20th	Night	18% 4 19% 37% 20% 2	760
	21st to end	Night	12% 3 29% 39% 15% 1	760
October	1st to 10th	Night	15% 4 26% 38% 15% 1	760
	11th to 20th	Night	11% 4 31% 38% 15% 1	760
	21st to end	Night	10% 7% 33% 38% 11% 1	836
November	1st to 10th	Night	16% 7% 32% 32% 12% 2	880
	11th to 20th	Night	11% 6% 41% 31% 10% 1	950
	21st to end	Night	7% 4 37% 39% 11% 2	950
December	1st to 10th	Night	11% 7% 30% 36% 14% 2	950
	11th to 20th	Night	8% 5% 35% 37% 13% 2	950
	21st to end	Night	11% 4 32% 37% 15% 2	1045

Page generated at 2024-11-03 00:11:23. Version ac07

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